DE102009015314A1 - Semiconductor laser device - Google Patents

Abstract

In the present case, a semiconductor laser device (1) is given. It comprises a first region (2), a second region comprising a planar region (4f) and a region (4g) protruding from the planar region, and an active region (3) located between the first (2) and second region is arranged, wherein a cover layer (5, 5a, 5b) containing a semiconductor material or a transparent conductive oxide, at least partially directly on the protruding region (4g) is arranged and the projecting region (4g) laterally surmounted.

Description

The The present application relates to a semiconductor laser device.

laser systems On the basis of AlGaInN will be of great importance for future technologies such as For example, the laser projection, data storage or printing technology and associated products. For one basic mode laser operation is a laser structure with a narrow Laser bar advantageous. The problem here, however, on the one hand the small pad of the p-contact connected to a narrow laser bar and on the other hand, the occurring in the GaN material system low electrical Conductivity. These Factors can for laser systems based on AlGaInN to a high operating voltage, a high power loss and lead to a high rate of aging.

Therefore there is one to be solved Object therein, a semiconductor laser device with improved electrical Specify properties.

These The object is achieved by a semiconductor laser device according to claim 1 solved.

advantageous Embodiments and developments of the semiconductor laser device are the subject of the dependent Claims.

According to one preferred embodiment the semiconductor laser device has a first region, a second region Area, which is a flat region and a region outstanding from the flat region has, and an active area between the first and the second region is arranged, wherein a cover layer, the contains a semiconductor material or a transparent conductive oxide, at least is arranged directly on the outstanding region and the outstanding region laterally surmounted.

One lateral overhanging the outstanding region through the top layer is given by that the lateral extent of the cover layer is greater than the lateral extent the outstanding region. The lateral direction preferably runs perpendicular to the direction in which the outstanding region is made the flat region stands out.

advantageously, are the materials contained in the top layer electrically conductive, so that the cover layer is electrically conductive and on the Covering an electrical current to be embossed into the salient region can. The cover layer can therefore be used as a connection layer for the second Serve area. For An electrical contact is expediently on the cover layer a metal layer is provided, in particular the cover layer corresponding or larger dimensions having. Due to the larger lateral Extent of the cover layer and the metal layer in comparison to outstanding region and the associated larger connection area due to a reduced contact resistance, a better current impression in the outstanding region possible, so that the operating voltage and the power loss are reduced can.

Further offers the extended top layer compared to a conventional, on the main surface the outstanding region limited cover layer the possibility a higher one Doping, so that also reduces the contact resistance can be.

The semiconductor laser device preferably contains a material based on nitride compound semiconductors, which in the present context means that at least one layer of the semiconductor laser device, in particular the first region, the second region or the active region, is a nitride compound semiconductor material, preferably Al _n Ga _m In _{1 -nm} N (in short: AlGaInN), where 0 ≤ n ≤ 1, 0 ≤ m ≤ 1 and n + m ≤ 1. This material does not necessarily have to have a mathematically exact composition according to the above formula. Rather, it may comprise one or more dopants as well as additional constituents which do not substantially alter the characteristic physical properties of the Al _n Ga _m In _1-nm N material. For the sake of simplicity, however, the above formula contains only the essential constituents of the crystal lattice (Al, Ga, In, N), even if these may be partially replaced by small amounts of other substances.

Especially contains the cover layer on nitride compound semiconductors based material.

Furthermore, the cover layer may contain a transparent conductive oxide or a combination of different transparent conductive oxides. Transparent conductive oxides ("TCO" for short) are transparent, conductive materials, usually metal oxides, such as zinc oxide, tin oxide, cadmium oxide, titanium oxide, indium oxide or indium tin oxide (ITO). In addition to binary metal oxygen compounds such as ZnO, SnO ₂ or In ₂ O _{3 also} include ternary metal oxygen compounds such as Zn ₂ SnO ₄ , CdSnO ₃ , ZnSnO ₃ , MgIn ₂ O ₄ , GaInO ₃ , Zn ₂ In ₂ O ₅ or In ₄ Sn ₃ O ₁₂ or mixtures of different transparent conductive oxides to the group of TCOs. Furthermore, the TCOs do not necessarily correspond to a stoichiometric composition and may also be p- or n-doped.

According to one preferred variant for the production of the semiconductor laser device become the first area, the active area and the second area successively grown epitaxially on a substrate. Especially the epitaxial growth takes place by means of metalorganic vapor phase epitaxy (MOVPE) or molecular beam epitaxy (MBE). The second area can be structured after epitaxial growth, in particular etched, so that educated the flat region and the outstanding region become. In particular, the outstanding region has a ridge-like Take shape, that is the outstanding region has an elongated, in cross-section preferably trapezoidal Build up.

Of the second area can provide different texture depths be. If the outstanding region is produced by etching, then the texture depth of the etch depth. The second area may, for example, only up to a cladding layer the semiconductor laser device are structured. advantageously, can this damages in an underlying waveguide layer can be avoided. however in this case the current expansion is greater than in the case of a structure depth, which extends to the active area.

present Therefore, depending on the requirements of the semiconductor laser device different structure depths in question.

at an advantageous embodiment of the semiconductor laser device the cover layer has grown epitaxially. With advantage the growth of the topcoat after the production of the outstanding Region instead. The cover layer can be grown in such a way that In particular, they have a main surface the outstanding region completely covered and in the lateral direction over the outstanding region extends.

For example The outstanding region can be used in two steps with a semiconductor material Overgrow MOVPE become. The two growth steps find in particular before and after peeling off a mask used to make the salient region instead of. Advantageously, can by overgrowing in two steps layers of different electrical and optical Properties are formed so that even the top layer, which is composed of these layers, different electrical and optical properties. For example, a lower, adjacent to side flanks of the outstanding region sublayer the cover layer contain a material that has a low electrical conductivity and one for a monomode laser operation suitable refractive index or a has a high degree of absorption. Furthermore, an upper, to a main area the outstanding region adjacent sub-layer of the top layer a material with a high electrical conductivity for optimal electrical Have contact. Furthermore, in the cover layer, a superlattice, in particular from AlInGaN / AlInGaN.

alternative Can the top layer be treated by MBE or HVPE (hydride gas phase epitaxy)? be generated. The advantage with these methods is the lower one Hydrogen entry into the laser structure compared to the production by MOVPE, so that in contrast to MOVPE no extra Activation is necessary.

at an alternative variant, the cover layer is evaporated, sputtered, spun or prepared by ion plating. This is less expensive than the overgrowth using MOVPE. Lower deposition temperatures may be advantageous reduce the temperature-induced defects in the active area. In particular, the cover layer is deposited by deposition of one or more TCOs formed. Advantageously, in a cover layer, the contains a TCO, the current expansion is reduced.

According to one preferred embodiment of the semiconductor laser device is the first region of a first conductivity type and the second Range of a second conductivity type. In particular, the first region is n-type, while the second region is p-type is.

Further For example, the second area may be nominally undoped at least in some areas be. Defects in the material cause a slight n-conductivity on.

Of the between the first and the second area arranged active area is intended in particular for generating radiation and has a pn junction on. This pn junction can in the simplest case by means of a p-type and an n-type Semiconductor layer may be formed, which adjoin one another directly. It is preferred between the p-type and the n-type layer is the actual radiation-producing layer Structure, for example in the form of a doped or undoped quantum structure, educated. The quantum structure can be considered a single quantum well structure (SQW, single quantum well) or multiple quantum well structure (MQW, Multiple quantum well) or as quantum wire or quantum dot structure be educated.

In an advantageous embodiment of the semiconductor laser device, the cover layer extends from a major surface of the protruding region at least to side flanks of the out projecting region. In particular, the cover layer adapts to the shape of the protruding region, that is to say the cover layer can also have a web-shaped form.

According to one Development of the semiconductor laser device is on the plane Region of the second area a passivation layer arranged. The passivation layer contains with advantage an electrically insulating material, in particular a electrically insulating nitride such as silicon nitride or aluminum nitride or an electrically insulating oxide such as silicon, zirconium, Aluminum or Hafnium oxide. These materials are in terms of their refractive indices particularly suitable, since by means of the resulting refractive index jump between the passivation layer and the adjacent second region an index-led Laser operation possible is. About that also allows the outstanding region a profit-driven laser operation.

at In an advantageous embodiment, the cover layer extends along the side flanks up to the passivation layer. In particular, covered the cover layer is a contact layer belonging to the outstanding region, which faces the cover layer. The contact surface between the cover layer and the contact layer is thus larger than in a mere application on the main surface the outstanding region. Thus, also the electrical contact improved between the cover layer and the contact layer. The Passivation layer, however, is located with advantage in one Area that is not primarily intended for Stromeinprägung, for example in the region of the cladding layer or a waveguide layer, the arranged on a side facing away from the cover layer of the contact layer are.

to damping higher Modes, the cover layer at least partially formed as an absorber be. The degree of absorption of the cover layer can change set the material composition within the cover layer become.

at In another embodiment, the cover layer extends from the main surface to the flat region. The topcoat can only be the flat region partially or completely cover. In this embodiment is thus not only about the outstanding region, but also over the flat region a current impression in the semiconductor laser device possible.

at complete Covering the flat region by the cover layer can in the edge area a Passivierungsschicht be arranged on the cover layer. alternative the flat region in the edge area can be uncovered. By both embodiments can on an additional Power stop layer can be omitted.

According to one another embodiment between the second region and the cover layer is a current stop layer arranged. The power stop layer may be at least partially on the be arranged in a flat region. Furthermore, the current stop layer can extend to the side flanks of the outstanding region.

The Power stop layer is electrically poorly conductive or electrically isolating, leaving a negligible electric current flows through them. For example, the Stromstoppschicht contain a dielectric material. Furthermore, can the current stop layer contain a nitride, for example AlN. Furthermore, the current-stop layer may consist of an undoped semiconductor layer, from a doped semiconductor layer of the first conductivity type or of a lightly doped semiconductor layer of the second conductivity type be formed. In particular, the current stop layer is epitaxial grew up.

The Power stop layer contains Advantageously, a material whose refractive index is so different from the Refractive index of the adjacent second area is different, that among other things an index-led Laser operation possible is.

Further For example, the current stop layer may be formed with a thickness at which damage and defects of the outstanding or even region, which are caused by the Structuring are balanced.

Further The power stop layer can be the side edges of the outstanding Protect the region from rapid aging.

As already mentioned, indicates the salient region according to an advantageous embodiment at the border to the cover layer on a contact layer. The contact layer at least partially borders directly on the cover layer. Preferably is the contact layer of the second conductivity type. In particular the contact layer p-type. For example, the contact layer may contain p-doped GaN.

Further the outstanding region may be adjacent to the contact layer Sheath layer have. This too is preferably of the second conductivity type. The cladding layer may be formed of p-doped AlInGaN.

According to one preferred embodiment, the cover layer serves as a further contact layer. In particular, the cover layer may be the same material as the underlying material Contact layer included.

following become embodiments a semiconductor laser device having a tunnel junction exhibit. Preferably, the tunnel junction is for electrical contacting of the second area. In particular, the tunnel junction arranged in the outstanding region.

It it is understood that the embodiments described below even in a semiconductor laser device without tunnel junction Application can be found and vice versa.

According to one preferred embodiment is the tunnel junction by means of a highly doped layer of the first conductivity type and a heavily doped layer of the second conductivity type educated. Thus, the second area is not continuous with the second one Conductivity type. Rather, the second area is only partially of the second conductivity type. It should be noted that the semiconductor layers of the tunnel junction not necessarily be homogeneously doped, since already a high Doping at the interface to the other semiconductor layer for forming a tunnel junction can suffice.

at An advantageous development is the tunnel junction between a layer of the first conductivity type and a layer of the second conductivity type, wherein preferably the layer of the first conductivity type on one of the active Area remote side of the tunnel junction is arranged while the Layer of the second conductivity type is arranged on a side facing the active area. Furthermore preferably contains the first conductivity type layer n-doped GaN, while the second conductivity type layer having p-doped GaN. In particular, both layers are located in the outstanding region. Thus, the tunnel junction buried in the outstanding region.

By the use of a buried tunnel junction may be above the outstanding region can be advantageously dispensed with magnesium-doped layers. This can be achieved on the side of the outstanding Region lower aging effects in the semiconductor laser device occur otherwise caused by the diffusion of magnesium can. Further This reduces the optical absorption and the series resistance.

According to one preferred embodiment is the cover layer, at least partially is located directly on the outstanding region and the outstanding Region laterally overhanging, of the first conductivity type.

Especially Preferably, the topcoat is epitaxial to the salient region grew up.

The Covering layer may be applied to the planar region such that the area exposed by the structuring next to the protruding one Region is filled by the topcoat.

For example For example, the cover layer may comprise n-doped AlInGaN, in particular n-doped Contain or consist of AlInN or n-doped AlGaN. alternative For example, the topcoat may contain or consist of an n-doped TCO.

in the The simplest case is the cover layer made of one material educated.

It but it is also possible to form the cover layer inhomogeneous, so that they have different materials having.

For example The cover layer may consist of layers of different electrical and optical properties. In particular, a adjacent to the planar region lower sub-layer of the cover layer a material with low electrical conductivity and matching refractive index for damping higher Modes included. Furthermore, one to the main surface of the outstanding Region adjacent upper sub-layer of the top layer has a high electrical conductivity for one have good electrical contact. For example, the lower Partial layer of an electrically insulating material, in particular an electrical insulating oxide such as a silicon oxide or an electrically insulating Nitride such as silicon nitride, contain or consist of. The upper Partial layer, however, can be made of an electrically conductive material be formed as an n-doped TCO. Furthermore, the lower sub-layer of a semiconductor material, such as an undoped AlGaN, and the upper sub-layer also made of a semiconductor material, formed about an n-doped AlInGaN, in particular an n-doped GaN be.

It but it is also possible that in the cover layer different semiconductor layers, such as several AlInGaN layers with different material composition, in particular with different Indium content, or different doping alternate. It is Furthermore, it is conceivable that the material composition, in particular the indium content, or the doping change from layer to layer continuously. Farther can be a superlattice, in particular from AlInGaN / AlInGaN.

In an advantageous variant, an attenuation for higher modes on the flat region is an Ab Sorber provided. This can be applied for example in the form of a structured layer directly on the planar region.

According to one preferred training is between the second area and the Cover layer provided a power stop layer. This can be, for example from the flat region to the side flanks of the outstanding ones Region. Thereby can the side edges are protected from rapid aging.

at a preferred embodiment is on one of the outstanding Region side facing away from the cover layer arranged a contact layer. Preferably the cover layer is covered over its entire area by the contact layer. The contact layer may contain, for example, n-doped GaN or consist of.

Further Preferably, the cover layer is on one of the protruding regions facing away from a flat main surface. The cover layer adapts not the shape of the outstanding region. She points in particular on the side facing away from the outstanding region on a larger surface as the main surface the outstanding region. The contact layer arranged on the cover layer thus also has a larger surface area as the main surface the outstanding region. As a result, the pad of the semiconductor laser device advantageously increased.

Preferably serves the cover layer in a semiconductor laser device with buried Tunnel junction as a cladding layer.

Further advantages and advantageous embodiments will become apparent from the following explanations in connection with the 1 to 17 ,

It demonstrate:

1 to 8th schematic cross-sectional views of various embodiments of a semiconductor laser device according to a first variant of the invention,

9 to 17 schematic cross-sectional views of various embodiments of a semiconductor laser device according to a second variant of the invention.

In the embodiments and figures are the same or equivalent components with the provided the same reference numerals.

1 shows a schematic cross-sectional view of a first embodiment of a semiconductor laser device 1 according to a first variant of the invention.

The semiconductor laser device 1 has a first area 2 and a second area between which an active area 3 arranged for generating radiation. The first area is preferred 2 n-type and the second range p-type. The second region may also be p-doped only in some regions and otherwise nominally undoped or even n-doped, so that it is partially n-type. The active area 3 is formed in particular in the form of a quantum structure, which may be undoped or doped. Here, a barrier layer is arranged in each case between two quantum well layers. Preferably, the active area is located 3 between two waveguide layers.

The first area 2 , the active area 3 and the second region include nitride compound semiconductor-based material, that is, they contain AlGaInN in particular.

The active area 3 are semiconductor layers belonging to the second region 4a and 4c downstream. In particular, the two semiconductor layers contain 4a . 4c p-doped GaN. Preferably, the two semiconductor layers serve 4a and 4c the wave guide. Particularly preferably, the two semiconductor layers differ 4a and 4c in the doping level, wherein in particular the semiconductor layer 4a less p-doped than the semiconductor layer 4c , For example, the semiconductor layer 4a nominally undoped.

Furthermore, the second region comprises an electron stop layer 4b that exist between the two semiconductor layers 4a . 4c is arranged and should prevent that in the first area 2 injected electrons penetrate too far into the second area. For example, the electron stop layer 4b AlGaInN included. Furthermore, the electron stop layer 4b preferably p-doped. In particular, the electron stop layer 4b be formed of p-doped AlGaN.

How out 1 As can be seen, the second area is structured so that it is a flat region 4f and one from the flat region 4f outstanding region 4g having. In particular, the outstanding region 4g web-shaped and has an elongated, trapezoidal in cross-section shape. By the outstanding region 4g is a profit-driven laser operation possible.

The outstanding region 4g includes on one of the active area 3 facing side a cladding layer 4d and on one of the active area 3 side facing away from a contact layer 4e , Preferably, the cladding layer contains 4d p-doped AlGaN, while the contact layer 4e from p-dopier GaN is formed. Furthermore, the cladding layer 4d have a superlattice of AlInGaN / AlInGaN. Furthermore, both the contact layer 4e as well as the cladding layer 4d be formed of a p-doped TCO.

The second region comprises the semiconductor layers 4a . 4c , the electron stop layer 4b , the coat layer 4d as well as the contact layer 4e ,

On the outstanding region 4g is a topcoat 5 arranged. This is at least partially in direct contact with the outstanding region 4g , The outstanding region 4g is from the topcoat 5 projected laterally.

At the in 1 illustrated embodiment, the cover layer fits 5 the shape of the outstanding region 4g on, that is, the cover layer has a web-shaped, elongated shape.

The cover layer 5 extends from a major area of the outstanding region 4g except for the side flanks. On the side edges contacted the cover layer 5 in particular the contact layer 4e ,

Advantageously, the top layer 5 the same material as the underlying contact layer 4e on, creating a good electrical contact between the cover layer 5 and the contact layer 4e is trained. In particular, the cover layer contains 5 p-doped GaN. Alternatively, the cover layer 5 be formed of a p-doped TCO.

Between the cover layer 5 and the second region is a passivation layer 6 , This is on the plane region 4f arranged and extends to the contact layer 4e , wherein the side edges of the cladding layer 4d from the passivation layer 6 are covered. The passivation layer 6 enables index-guided laser operation. The passivation layer 6 may comprise an electrically insulating material, in particular an electrically insulating nitride such as silicon nitride or aluminum nitride or an electrically insulating oxide such as a silicon, aluminum or hafnium oxide.

On the uncovered surface of the topcoat 5 In particular, a connection layer made of metal (not shown) can be applied over the whole area. The semiconductor laser device 1 in this case has a comparatively large-area p-contact. Compared to a conventional Ridgelaser with Ridgebreiten between 1 .mu.m and 2 .mu.m can in the in 1 illustrated semiconductor laser device 1 the contact resistance and the operating voltage are advantageously reduced. The extended top layer 5 also offers the possibility of a higher p-doping, so that also the contact resistance can be reduced thereby.

For the production of in 1 illustrated semiconductor laser device 1 become the first area 2 , the active area 3 and the second region is grown epitaxially in succession on a suitable substrate (not shown). Subsequently, the second region is structured such that it forms the plane region 4f and those from the flat region 4f outstanding region 4g having. In particular, the second area for making the outstanding region 4g etched.

Preferably, the second region is removed to the p-waveguide layer around the protruding region 4g train. However, it is also possible, the second area only to the cladding layer 4d to remove. Although this can be expected with a larger current expansion. But less damage occurs in the p-waveguide layer.

Alternatively, the second region may be up to the electron stop layer 4b or even up to the active area 3 be removed. Advantageously, in this case occurs a lower current expansion.

After the production of the outstanding region 4g becomes the passivation layer 6 on the flat region 4f applied.

In a subsequent step, the contact layer 4e with the topcoat 5 overgrown.

2 shows a schematic cross-sectional view of a second embodiment of a semiconductor laser device 1 according to a first variant of the invention.

The semiconductor laser device 1 according to 2 has a similar structure as in 1 illustrated semiconductor laser device. However, the passivation layer is sufficient 6 not up to the contact layer 4e , It covers the side edges of the cladding layer 4d only partially. The cover layer 5 that conform to the passivation layer 6 also covers areas of the cladding layer 4d ,

In this case, the arranged on the side edges cover layer 5 serve as an absorber for damping higher modes.

Otherwise, the in 2 illustrated semiconductor laser device 1 all in conjunction with 1 have mentioned advantages and refinements.

In contrast to the embodiments of the 1 and 2 have the in the 3 and 4 illustrated third and fourth embodiments of a semiconductor laser device 1 no passivation layer between the second region and the cover layer 5 on. The cover layer 5 extends from a major area of the outstanding region 4g along the side flanks to the flat region 4f , The cover layer 5 can serve as an absorber.

In particular, in these embodiments, the cladding layer contains 4d AlInGaN. For example, the second semiconductor layer 4c p-doped GaN, while the cladding layer 4d is formed from p-doped AlInGaN. Furthermore, it is possible that the second semiconductor layer 4c p-doped InGaN contains while the cladding layer 4d p-doped AlInGaN has.

Here, the refractive index difference between cover layer is 5 and outstanding region 4g less than the refractive index difference between a typical passivation layer and the protruding region 4g , Therefore, in the embodiments of the 3 and 4 an index-guided laser operation difficult to implement than in the case of the embodiments of the 1 and 2 , An improvement can be made by a passivation layer 6 in the marginal area of the top layer 5 is applied (see. 3 ), or by a spacing of the cover layer 5 from the edge of the semiconductor laser device 1 (see. 4 ) be achieved. Furthermore, in these embodiments, an additional power stop layer can be dispensed with.

5 shows a fifth embodiment of a semiconductor laser device 1 , In this case, the cover layer extends 5 from the main area of the outstanding region 4g along the side flanks to the flat region 4f and is in direct contact with the second semiconductor layer 4c , On the side flanks of the outstanding region 4g is below the topcoat 5 a power stop layer 7 arranged to the level region 4f enough. This protects the outstanding region 4g severe degradation and also improves index-guided laser operation.

The power stop layer 7 may contain a dielectric material. Furthermore, the current stop layer 7 have a nitride such as AlN. Furthermore, the current stop layer 7 an undoped or n-doped semiconductor layer grown epitaxially.

This in 5 illustrated embodiment may in accordance with the embodiments of the 3 and 4 be modified, that is, the top layer 5 can be in the edge area with a passivation layer 6 be provided or the plane region 4f can be in the edge area of the topcoat 5 remain uncovered.

At the in 6 illustrated sixth embodiment of a semiconductor laser device 1 is between the topcoat 5 and the flat region 4f a power stop layer 7 arranged. This is in direct contact with the second semiconductor layer 4c and covers only a negligible part of the outstanding region 4g , In this embodiment, the cladding layer contains 4d AlInGaN. In particular, the cladding layer 4d be formed of p-doped AlInGaN.

Through the power stop layer 7 is the semiconductor layer 4c opposite the cover layer 5 well insulated. The flow of electricity can pass through the side flanks of the outstanding region 4g through. By means of the current stop layer 7 , which in particular has grown epitaxially, may be covered by the structuring of the second area caused damage or other unevenness.

Also in 6 illustrated embodiment, in accordance with the Ausführungsbesipielen the 3 and 4 be modified, that is, the top layer 5 can be in the edge area with a passivation layer 6 be provided or the plane region 4f can be in the edge area of the topcoat 5 remain uncovered.

At the in 7 illustrated seventh embodiment of a semiconductor laser device 1 is between the topcoat 5 and the flat region 4f as with the in 6 illustrated semiconductor laser device 1 a power stop layer 7 arranged. In addition, the power stop layer covers 7 here the side flanks of the outstanding region 4g , In this embodiment, the cladding layer contains 4d no indium. In particular, the cladding layer 4d be formed of p-doped AlGaN.

Also in 7 illustrated embodiment may in accordance with the embodiments of the 3 and 4 be modified, that is, the top layer 5 can be provided in the border area with a passivation layer or the flat region 4f can be in the edge area of the topcoat 5 remain uncovered.

At the in 8th illustrated eighth embodiment of a semiconductor laser device 1 that is between the topcoat 5 and the flat region 4f a power stop layer 7 and wherein the current stop layer 7 over the side flanks to the main area of the outstanding region 4g extends, contains the cladding layer 4d no indium, but is formed in particular of p-doped AlGaN. The power stop layer 7 can be made of AlGaN. In particular, the electricity stop layer 7 in this embodiment, in the region of the major surface of the salient region 4g p-doped. Preferably, a doping is selected which is smaller than 5 × 10 ¹⁷ / cm ³ . Mg can be used as the p-type dopant. For example, the region of the current stop layer adjoining the main surface 7 by diffusion from the contact layer 4e be enriched with the p-type dopant.

The cover layer 5 is advantageously formed partially as an absorber.

Also in 8th illustrated embodiment may in accordance with the embodiments of the 3 and 4 be modified, that is, the top layer 5 can be provided in the border area with a passivation layer or the flat region 4f can be in the edge area of the topcoat 5 remain uncovered.

Except for the mentioned differences, those in the 3 to 8th illustrated semiconductor laser devices 1 all in connection with 1 have mentioned advantages and refinements.

9 shows a schematic cross-sectional view of a first embodiment of a semiconductor laser device 1 according to a second variant of the invention.

The semiconductor laser device 1 has a first area 2 and a second area between which an active area 3 arranged for generating radiation. The first region is preferred 2 n-type. The second region is at least partially p-type. The active area 3 is formed in particular in the form of a quantum structure, which may be undoped or doped. Here, a barrier layer is arranged in each case between two quantum well layers. Preferably, the active area is located 3 between two waveguide layers.

The first area 2 , the active area 3 and the second region advantageously comprise nitride compound semiconductor-based material, that is, they contain, in particular, AlGaInN.

The active area 3 are semiconductor layers belonging to the second region 4a and 4c downstream. In particular, the two semiconductor layers contain 4a . 4c p-doped GaN. In addition, for example, the semiconductor layer 4a nominally undoped. Furthermore, the second region comprises one between the two semiconductor layers 4a . 4c arranged electron stop layer 4b that should prevent that in the first area 2 injected electrons penetrate too far into the second area. As already related to 1 mentioned, serve the semiconductor layers 4a . 4c especially for waveguiding.

How out 9 As can be seen, the second area is structured so that it is a flat region 4f and one from the flat region 4f outstanding region 4g having. In particular, the outstanding region 4g web-shaped and has an elongated, trapezoidal in cross-section shape. By the outstanding region 4g is a profit-driven laser operation possible.

The outstanding region 4g includes on one of the active area 3 facing side, a third semiconductor layer 4h and on one of the active area 3 opposite side, a fourth semiconductor layer 4y , The third semiconductor layer preferably contains 4h p-doped GaN, while the fourth semiconductor layer 4y is formed of n-doped GaN.

Between the third semiconductor layer 4h and the fourth semiconductor layer 4y is a tunnel crossing 4i arranged. The tunnel crossing 4i is in the outstanding region 4g buried. The tunnel crossing 4i may be formed by means of a highly doped p-type layer and a heavily doped n-type layer. By using a buried tunnel junction can be located above the salient region 4g can be dispensed with advantage on magnesium-doped layers. As a result, on the side of the outstanding region 4g lower aging effects in the semiconductor laser device 1 which may otherwise be induced by the diffusion of magnesium. Furthermore, this reduces the optical absorption and the series resistance.

The second region comprises the semiconductor layers 4a . 4c . 4h and 4y as well as the tunnel crossing 4i , Furthermore, the second region comprises the electron stop layer 4b ,

On the outstanding region 4g is a topcoat 5 arranged. This covers a main surface as well as side flanks of the outstanding region 4g , The outstanding region 4g is from the topcoat 5 projected laterally.

The cover layer 5 adapts to the shape of the outstanding region 4g not on. Rather, the topcoat is 5 so on the flat region 4f applied to the area exposed by the structuring next to the salient region 4g from the topcoat 5 is filled. The cover layer 5 extends from the main area of the outstanding region 4g to the flat region 4f and preferably covers them completely.

On one of the outstanding region 4g opposite side has the cover layer 5 a level Main surface on. The flat major surface is advantageously larger than the major surface of the salient region 4g ,

Preferably, the cover layer is 5 n-type. It can be formed from n-doped AlInGaN, for example from n-doped AlGaN or AlInN. In particular, the cover layer serves 5 as a cladding layer.

On the flat main surface of the cover layer 5 is a contact layer 8th arranged. At the in 9 illustrated embodiment, the cover layer 5 from the contact layer 8th completely covered. This allows good electrical contact between the cover layer 5 and the contact layer 8th , For example, the contact layer 8th n-doped GaN included.

On the uncovered surface of the contact layer 8th In particular, a connection layer made of metal (not shown) can be applied over the whole area. The semiconductor laser device 1 in this case has a large-area p-side contact.

For the production of in 9 illustrated semiconductor laser device 1 become the first area 2 , the active area 3 and the second region is grown epitaxially in succession on a suitable substrate (not shown). Subsequently, the second region is structured such that it forms the plane region 4f and those from the flat region 4f outstanding region 4g having. In particular, the second area for making the outstanding region 4g etched.

Preferably, the second region is removed to the p-waveguide layer around the protruding region 4g train. However, it is also possible to use the second region only up to the third semiconductor layer 4d to remove. Although this can be expected with a larger current expansion. But less damage occurs in the p-waveguide layer. Alternatively, the second region may be up to the electron stop layer 4b or even up to the active area 3 be removed. Advantageously, in this case occurs a lower current expansion.

After the production of the outstanding region 4g can the plane region 4f and the outstanding region 4g with the topcoat 5 overgrown. Overgrowth can be done using MOVPE, HVPE or MBE. An advantage of the last two methods is that the topcoat 5 In this case hydrogen-free can be applied so that no hydrogen diffusion into the highly doped p-type layer of the tunnel junction 4i he follows. On the other hand, in the production by MOVPE hydrogen in the tunnel junction 4i penetrate, whereby the highly doped p-type layer can be passivated.

On the flat main surface of the cover layer 5 may after making the topcoat 5 the contact layer 8th be grown epitaxially.

10 shows a schematic cross-sectional view of a second embodiment of a semiconductor laser device 1 according to the second variant of the invention.

The semiconductor laser device 1 according to 10 has a similar structure as in 9 illustrated semiconductor laser device. However, the second region includes the semiconductor laser device 1 additionally a marking layer 4k , The marking layer 4k is provided for the location of the tunnel junction 4i to highlight, so that during the structuring of the second area, it is clear how far the structuring must be done. This allows precise control of the structure depth.

After structuring, the marking layer is 4k Part of the outstanding region 4g and is preferably located between the third semiconductor layer 4h and the tunnel crossing 4i , For example, the marking layer 4k p-doped AlGaInN, in particular p-doped AlGaN included.

In the 10 illustrated semiconductor laser device 1 In addition, all in conjunction with 9 have mentioned advantages and refinements.

11 shows a schematic cross-sectional view of a third embodiment of a semiconductor laser device 1 according to the second variant of the invention.

The semiconductor laser device 1 according to 11 has a similar structure as in 9 illustrated semiconductor laser device. However, the top coat is 5 not like in the 9 illustrated embodiment formed continuously from a material system. Rather, the material composition can be within the cover layer 5 to change. This can be realized in various ways.

For example, the cover layer may 5 composed of several AlInGaN layers whose indium content varies. In addition, the n-type doping may change. The layers of different composition or doping may alternate. Alternatively, the composition or doping of the layers may change continuously. Finally, the topcoat can 5 have a superlattice of AlInGaN / AlInGaN.

For a cover layer 5 that is an inhomogeneous ne material composition, advantageously, the refractive index can be adjusted independently of the lattice constant. In particular, the cover layer 5 lattice-matched, that is applied low-stress.

In the 11 illustrated semiconductor laser device 1 can all except in connection with the differences mentioned 9 have mentioned advantages and refinements.

12 shows a schematic cross-sectional view of a fourth embodiment of a semiconductor laser device 1 according to the second variant of the invention.

The semiconductor laser device 1 according to 12 has a similar structure as in 9 illustrated semiconductor laser device. However, the top coat is 5 not like in the 9 illustrated embodiment formed of a semiconductor material. Rather, the topcoat exhibits 5 a TCO that is n-doped. This can be dispensed with an additional contact layer. On the top layer 5 can be arranged directly a metal connection layer.

Compared to a cover layer produced by means of MOVPE, the deposition of the TCO-containing cover layer takes place 5 less expensive. In addition, the lower deposition temperature can cause temperature-induced defects, especially in the active region 3 to be reduced.

In the 12 illustrated semiconductor laser device 1 can all except in connection with the differences mentioned 9 have mentioned advantages and refinements.

13 shows a schematic cross-sectional view of a fifth embodiment of a semiconductor laser device 1 according to the second variant of the invention.

Like that in 9 illustrated embodiment, the semiconductor laser device 1 according to 13 a cover layer 5 of a semiconductor material, preferably epitaxially on the planar region 4f and the outstanding region 4g grew up.

Between the cover layer 5 and the second region is a passivation layer 6 arranged. This advantageously contains an electrically insulating oxide, in particular a silicon oxide. The passivation layer 6 may also be formed of an electrically insulating nitride such as silicon nitride. The passivation layer 6 extends from the plane region 4f down to the side flanks of the outstanding region 4g , where preferably neither the planar region 4f still the side edges are completely covered by the passivation layer.

In the area of the side edges is between the passivation layer 6 and the topcoat 5 an air gap 9 intended. By means of the thereby induced refractive index jump at the transition from the passivation layer 6 or second area to the air gap 9 is a good optical guidance possible.

The air gap 9 can be generated, for example, that the cover layer 5 on the areas of the plane region 4f and the outstanding region 4g grown, which allow a crystalline growth, while due to the typically amorphous material of the passivation layer 6 In this area, no cohesive growth is possible and thus the air gap 9 is trained.

In the 13 illustrated semiconductor laser device 1 can all except in connection with the differences mentioned 9 have mentioned advantages and refinements.

14 shows a schematic cross-sectional view of a sixth embodiment of a semiconductor laser device 1 according to the second variant of the invention.

The semiconductor laser device 1 according to 14 has a similar structure as in 9 illustrated semiconductor laser device. However, it is on the flat region 4f an absorber 10 arranged. The absorber 10 is in the form of a structured layer on the plane region 4f applied. Advantageously, by means of the absorber 10 higher modes are attenuated, so that a laser operation in the fundamental mode is possible. For the absorber 10 suitable materials include, for example, high melting point metals such as W, Ta, Re, Rh or Pt. Further, dielectric materials such as silicon oxide compounds may be used to advantage.

In the 14 illustrated semiconductor laser device 1 can all except in connection with the differences mentioned 9 have mentioned advantages and refinements.

15 shows a schematic cross-sectional view of a seventh embodiment of a semiconductor laser device 1 according to the second variant of the invention.

In this embodiment, the pattern depth is larger than in the previously described embodiments according to FIG second variant. The second area is through the electron stop layer 4b through to almost the active area 3 ablated. Advantageously, by means of the larger structure depth, the current expansion can be greatly reduced.

On the flat region 4f and the side flanks of the outstanding region 4g is a power stop layer 7 arranged. This allows the passivation of the outstanding region 4g , which is more susceptible to electrical problems due to the greater structural depth. The power stop layer 7 contains an AlInGaN with a high Al content. The power stop layer 7 may be undoped, n-doped, or slightly p-doped.

The cover layer consists of two different partial layers 5a and 5b together. The lower part layer 5a covers the flat region 4f and reaches almost to the tunnel crossing 4i , Preferably, the lower sub-layer contains 5a a material with low electrical conductivity. Furthermore, the material of the lower part of the layer 5a advantageously a refractive index which is less than the refractive index of the semiconductor layer 4a , For example, contains the lower sub-layer 5a undoped AlGaN, while the semiconductor layer 4a contains p-doped GaN. The upper part layer 5b is on the lower part layer 5a and the outstanding region 4g arranged. Preferably, the upper sublayer 5b a high electrical conductivity for a good electrical contact. The upper part layer 5b contains, for example, n-doped AlInGaN, in particular n-doped AlGaN, n-doped AlInN or n-doped GaN.

The power stop layer 7 and the lower part layer 5a can after the education of the outstanding region 4g be prepared before the generation of the outstanding region 4g used mask is removed. After the production of the current stop layer 7 and the lower part layer 5a You can remove the mask and the upper part of the layer 5b to be raised.

In the 15 illustrated semiconductor laser device 1 can all except in connection with the differences mentioned 9 have mentioned advantages and refinements.

16 shows a schematic cross-sectional view of an eighth embodiment of a semiconductor laser device 1 according to the second variant of the invention.

The semiconductor laser device 1 has as the embodiment of 15 a structure depth that is almost up to the active area 3 enough.

To passivate the outstanding region 4g the cover layer has a lower partial layer 5a on, which serves as a passivation layer. This is on the plane region 4f arranged and extends to the fourth semiconductor layer 4y , The lower part layer 5a covers the side flanks of the outstanding region 4g almost complete. Preferably, the lower sub-layer contains 5a an electrically insulating oxide such as a silicon oxide. But it is also conceivable that the lower part of the layer 5a an electrically insulating nitride such as silicon nitride.

On the lower part layer 5a and the outstanding region 4g is the upper part layer 5b the cover layer arranged. This advantageously contains an n-doped TCO. As already mentioned, the production of a layer of TCO is less complicated than the MOVPE overgrowth. In addition, the lower deposition temperature causes less temperature-induced defects to occur.

In the 16 illustrated semiconductor laser device 1 can all except in connection with the differences mentioned 9 . 12 and 15 have mentioned advantages and refinements.

17 shows a schematic cross-sectional view of a ninth embodiment of a semiconductor laser device 1 according to the second variant of the invention.

The illustrated semiconductor laser device 1 has a similar structure as in 9 illustrated semiconductor laser device. However, the structure depth is smaller than in the case of the embodiments of 9 to 16 , The second area is only up to the tunnel crossing 4i structured. This occurs in the active area 3 and in the second area less damage. However, a larger current expansion takes place.

The The invention is not by the description based on the embodiments limited. Much more For example, the invention includes every novel feature as well as every combination of features, in particular any combination of features in the claims includes, even if this feature or this combination itself not explicitly stated in the patent claims or exemplary embodiments is.

Claims (15)

Semiconductor laser device ( 1 ) with a first area ( 2 ), - a second region, which is a flat region ( 4f ) and an out-of-flat region ( 4g ), and with an active area ( 3 ), which between the first ( 2 ) and the second region, wherein a cover layer ( 5 . 5a . 5b ) containing a semiconductor material or a transparent conductive oxide, at least partially directly on the projecting region ( 4g ) and the outstanding region ( 4g ) projected laterally. Semiconductor laser device ( 1 ) according to claim 1, wherein the cover layer epitaxially ( 5 . 5a . 5b ) grew up. Semiconductor laser device ( 1 ) according to claim 1 or 2, wherein the first region ( 2 ) of a first conductivity type and the second region at least partially of a second conductivity type. Semiconductor laser device ( 1 ) according to claim 3, wherein the cover layer ( 5 . 5a . 5b ) from one major surface at least to side flanks of the salient region ( 4g ) and the shape of the salient region ( 4g ) adapts. Semiconductor laser device ( 1 ) according to claim 4, wherein on the plane region ( 4f ) of the second area a passivation layer ( 6 ), and the top layer ( 5 . 5a . 5b ) along the side flanks up to the passivation layer ( 6 ). Semiconductor laser device ( 1 ) according to claim 4, wherein the cover layer ( 5 . 5a . 5b ) from the main surface to the flat region ( 4f ). Semiconductor laser device ( 1 ) according to claim 6, wherein between the second region and the cover layer ( 5 . 5a . 5b ) a current stop layer ( 7 ) is arranged. Semiconductor laser device ( 1 ) according to claim 7, wherein the current stop layer ( 7 ) has grown epitaxially. Semiconductor laser device ( 1 ) according to any one of claims 3 to 8, wherein the salient region ( 4g ) at least partially directly to the cover layer ( 5 . 5a . 5b ) adjacent contact layer ( 4e ) of the second conductivity type. Semiconductor laser device ( 1 ) according to claim 9, wherein the salient region ( 4g ) one to the contact layer ( 4e ) adjacent cladding layer ( 4d ) of the second conductivity type. Semiconductor laser device ( 1 ) according to one of claims 3 to 10, wherein the cover layer ( 5 . 5a . 5b ) serves as another contact layer. Semiconductor laser device ( 1 ) according to claim 1 or 2, wherein the first region ( 2 ) of a first conductivity type and the second region is only partially of a second conductivity type, and wherein the protruding region ( 4g ) a tunnel junction ( 4i ) having. Semiconductor laser device ( 1 ) according to claim 12, wherein the cover layer ( 5 . 5a . 5b ) serves as a cladding layer. Semiconductor laser device ( 1 ) according to claim 12, wherein the cover layer ( 5 . 5a . 5b ) on one of the outstanding regions ( 4g ) facing away from a flat main surface. Semiconductor laser device ( 1 ) according to any one of the preceding claims, wherein the salient region ( 4g ) has a web-like shape.