WO2002013276A1 - A memory device and a memory array - Google Patents
A memory device and a memory array Download PDFInfo
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- WO2002013276A1 WO2002013276A1 PCT/GB2000/003416 GB0003416W WO0213276A1 WO 2002013276 A1 WO2002013276 A1 WO 2002013276A1 GB 0003416 W GB0003416 W GB 0003416W WO 0213276 A1 WO0213276 A1 WO 0213276A1
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
- H01L29/76—Unipolar devices, e.g. field effect transistors
- H01L29/7613—Single electron transistors; Coulomb blockade devices
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
- G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
- G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
- G11C11/161—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
- G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
- G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
- G11C11/165—Auxiliary circuits
- G11C11/1675—Writing or programming circuits or methods
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/12—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
- H01L29/122—Single quantum well structures
- H01L29/127—Quantum box structures
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/12—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
- H01L29/22—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only AIIBVI compounds
- H01L29/221—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only AIIBVI compounds including two or more compounds, e.g. alloys
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B61/00—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C2216/00—Indexing scheme relating to G11C16/00 and subgroups, for features not directly covered by these groups
- G11C2216/02—Structural aspects of erasable programmable read-only memories
- G11C2216/08—Nonvolatile memory wherein data storage is accomplished by storing relatively few electrons in the storage layer, i.e. single electron memory
Definitions
- This invention relates to a memory device and a memory array.
- DRAM dynamic random access memory
- An aspect of the present invention provides a spin detector comprising a three-dimensionally quantum confined region arranged to operate in the Coulomb blockage regime coupled by tunnel barriers to input and output Fermi leads having g-factors considerably larger than the quantum confined region whereby application of a magnetic field causes Zeeman splitting in the quantum confined region and the Fermi leads with the Zeeman splitting in the leads being considerably greater than that in the quantum confined region, whereby a current applied to the input lead is spin-polarised and conduction through the quantum confined region occurs primarily by sequential tunnelling of an electron having the same spin polarisation as the leads.
- the spin polarisation of an electron in the quantum confined region may be controlled by electron spin resonance techniques using AC magnetic field pulses so as to induce a Rabi spin-flop which spin-flop exists for sufficiently long time to enable the spin state to be used to store data so that one of spin up and spin down represents "0" and the other represents "1".
- the spin state of the memory device may be determined by detecting the current through the quantum confined region which will be considerably higher when the spin state of the quantum confined region coincides with that of the spin polarised Fermi leads .
- a two-dimensional or even three-dimensional array of such memory devices may be produced to provide a dynamic random access memory device.
- a non-volatile memory device may be provided by arranging a hard magnetic layer, magnetic nano-particle, magnetic impurity or layer of nuclear spins providing an Overhauser field in close proximity to the quantum confined region.
- the present invention provides a switch having a three-dimensionally quantum confined region coupled by tunnel barriers to input and output Fermi leads such that the quantum confined region is arranged to operate in the Coulomb blockage regime and the g-factors of the Fermi leads are considerably higher than that of the quantum confined region such that when, in use, Zeeman splitting is induced, the Zeeman splitting in the Fermi leads is considerably greater than in the quantum confined region and spin polarisation occurs in the input and output leads , and having means for controlling the direction of spin polarisation of the input and output leads whereby, when the polarisations of the input and output leads are the same, conduction can occur by sequential tunnelling of an electron through the quantum confined region whereas when the spin polarisations of the input and output leads are opposite, conduction is inhibited.
- Figure 1 shows a very diagrammatic functional diagram of a memory embodying the invention
- Figure 2 shows a side view of the memory shown in Figure 1 ;
- Figure 3 shows a very diagrammatic cross-sectional view through one example of a memory device suitable for use in the memory shown in Figure 1 and Figure 2.
- Figure 4 shows a representational diagram for illustrating the operation of a memory device embodying the invention
- Figures 5 to 8 show conduction band energy level diagrams for explaining the principle of operation of a memory device embodying the present invention
- Figures 9a and 9b show respective conduction band energy level diagrams for illustrating the effect on a memory device embodying the invention of an AC magnetic field inducing electron spin resonance;
- Figure 10 shows a graph of current (I) against time (t) for illustrating the change in current resulting from the application of an alternating magnetic field inducing electron spin resonance to a memory device embodying the present invention.
- Figure 11 shows a functional block diagram illustrating one example of a two-dimensional memory array embodying the present invention
- Figure 12 shows a simplified top plan view of part of the memory array shown in Figure 11 to illustrate a possible layout
- Figure 13 shows cross-sectional view similar to Figure 3 illustrating another example of a memory device embodying the invention
- Figure 14 shows a functional diagram of a two-dimensional memory array using the memory device shown in Figure 13;
- Figure 15 shows a cross-sectional view similar to Figure 13 for illustrating a modification of the memory device shown in Figure 13;
- Figure 16 shows a functional diagram of another example of a two-dimensional memory array embodying the invention.
- Figures 17 and 18 show conduction band energy level diagrams for illustrating operation of a current switch embodying the present invention.
- FIG. 1 there is shown a simplified diagram for illustrating functional elements of a memory device 1 embodying the invention.
- the memory device 1 comprises a three-dimensionally quantum confined region in the form of a quantum dot in a quantum dot region 2 coupled by tunnel barriers TBl and TB2 to respective input and output Fermi leads 3 and 4 formed by highly doped semiconductor regions.
- the quantum dot is configured to operate in the Coulomb blockade regime which is discussed in detail in, for example, section 2.1 at pages 114 to 118 of the chapter entitled “Electron transport in quantum dots” by Kouwenhoven et al in the review text book entitled “Mesoscopic Electron Transport” edited by Sohn, Kouwenhoven, and Sch ⁇ n (ISBN No. 0-7923-4737-4).
- the quantum dot region 2 and Fermi leads 3 and 4 are formed of materials such that the Fermi leads 3 and 4 have a g-factor considerably greater than that of the quantum dot region 2.
- a DC magnetic field generator ( Figure 2 ) 5 is provided for inducing Zeeman splitting in the quantum dot and Fermi leads 3 and 4 and an AC magnetic field generator 6 is provided for generating an AC magnetic field perpendicular to the DC magnetic field.
- the input and output Fermi leads 3 and 4 are coupled to respective contacts Ll and L2 between which a voltage source VS is coupled.
- An annular gate G contacts the quantum dot region 2 and is coupled to a gate voltage source GV.
- a current sensor CS is coupled to contact L2 to sense the current through the device 1.
- the device 1 may be manufactured using conventional quantum dot manufacturing techniques such as, for example MBE (molecular beam epitaxy) or MOCVD (metal organic chemical vapour deposition) and lithographic techniques such as x-ray or electron beam lithography.
- the DC magnetic field generator 5 is required to generate a homogenous DC magnetic field of the order of at most a few Tesla.
- the DC magnetic field generator 5 may, therefore, consist of a commercially available nanomagnet.
- the DC magnetic field generator 5 may be provided in a manner similar to that used for IBM magnetic storage discs or dysprosium dots may be used. Where nanomagnets or dysprosium dots are used, then these may be integrated with the device 1.
- a superconducting magnet may be used as the DC magnetic field generator 5.
- the AC magnetic field generator 6 is a standard AC magnetic field generator used for electron spin resonance techniques that is capable of generating an AC magnetic field pulse.
- the magnetic fields required may be provided by, for example, permanent magnets or even electrically driven solenoids.
- the device 1 may be manufactured using standard quantum dot fabrication techniques.
- Figure 3 shows a very diagrammatic cross-sectional view through part of a semiconductor body 10 to illustrate one example of a structure that may be used for the device.
- the semiconductor body 10 comprises a substrate 11 generally an intrinsic (that is not intentionally doped) Gallium Arsenide (GaAs) substrate 11 on to which may be grown, as is well known in the MBE and
- Superlattice structure SL to provide a clean relatively defect free surface S.
- Alternate layers of a magnetic II-VI, a non-magnetic III-V and a magnetic II-VI material are then grown on the surface S using standard MOCVD or MBE techniques. These layers are then patterned using standard vertical quantum dot defining lithographic techniques to define a column C providing first and second n conductivity type II-VI regions defining the Fermi leads 3 and 4 separated by a III-V region defining the quantum dot region 2. As can be seen from Figure 3, the etching process does not continue all the way through the bottom II-VI layer, rather a portion 3a of the bottom II-VI layer remains.
- a chromium layer 12 is deposited to enable ohmic contact to the Fermi lead 3 followed by an insulating material (generally silicon dioxide) layer 13 followed by a further metallic (generally chromium) layer 14 and a further insulating layer 15. Vias VI and V2 are etched through these layers in known manner and metallisation (again generally chromium) deposited to define the first contact Ll contacting the chromium layer 12, the gate G contacting the chromium layer 14 and the contact L2 contacting the Fermi lead 4.
- the II-VI material is an n conductivity type Beryllium Manganese Zinc Selenide alloy (Be x Mn y Zni-. x . y Se) having a composition such that the II-VI material is lattice-matched to the III-V material forming the quantum dot region 2 which is, in this example, n conductivity type Gallium Arsenide (GaAs).
- the II-VI alloy may have the composition Be 0 . 07 Mn o . o3 Zn 0 . 9 Se.
- a Beryllium Manganese Zinc Selenide alloy is selected to form the Fermi leads or regions 3 and 4 because, as described in a Letter to Nature published in Nature Volume 402, 16 December 1999 at pages 787 to 789 by Fiederling et al , this material has been shown to provide efficient transport of a spin polarised current and, moreover, efficient injection of that spin polarised current into a non-magnetic semiconductor material such as Gallium Arsenide.
- the column C may have a circular cross section with a diameter of about 0.5 micrometers which, as will be understood by the person skilled in the art, is not sufficiently small to define a quantum dot within the quantum dot region 2.
- confinement in the lateral direction in Figure 3 may be achieved by applying a voltage to the gate G to define within the quantum dot region 2 a quantum dot having a diameter of about 50 nanometers.
- the quantum dot is required to operate in the quantum Coulomb blockade regime which requires that:
- K B is Boltzmann's constant
- T is temperature
- ⁇ E is the difference between energy levels in a quantum dot
- e is the electron charge
- C is the capacitance of the quantum dot
- the " , " means that the inequality is satisfied for both components on the right hand side, that is:
- the quantised level spacing and Coulomb charging energy will be of the order of 1 meV (milli electron volt) so that, in this example, the device should be operated at liquid Helium temperatures (a few Kelvin) using conventional low temperature generation techniques. It will, however, be appreciated by those skilled in the art that scaling down the size of the quantum dot by a factor of 10 will raise the necessary temperature by a factor of 100 thus allowing operation at room temperature.
- Figure 4 shows a schematic representation of the device 1 when a voltage has been applied to the annular gate G to provide the necessary further confinement to define a quantum dot 2a within the quantum dot region.
- Figure 4 also shows the relative orientation of the DC magnetic field B dc (into the plane of the paper in Figure 4 ) and AC magnetic field B ac when applied by the DC magnetic field generator 5 and AC magnetic field generator 6, respectively.
- u ⁇ and ⁇ 2 represent the chemical potentials of the Fermi leads 3 and 4 which, in the Coulomb blockade regime with one electron in the uppermost ground state of the quantum dot 2a, is related to the voltage V 12 applied between the contacts Ll and L2 as follows:
- V ⁇ , 2 ( ⁇ - ⁇ 2 ) /e (2)
- Figure 5 shows for the purpose of illustration the one electron 20 in the uppermost ground state of the quantum dot 2a as having spin state up.
- ⁇ B is the Bohr magneton and B is the applied DC magnetic field.
- Figure 6a shows the case where the uppermost electron 20 in the quantum dot has a spin state up whilst Figure 6b shows the case where the uppermost electron 20a has a spin state down.
- the direction of the DC magnetic field B dc is such that the electron 20 in spin state up has a lower energy than the electron 20a in spin state down.
- both the singlet E s and triplet energy levels are split. However, for the sake of convenience, only the lower level E ⁇ + triplet state is shown in Figures 6a and 6b.
- the energy of the ground state lower energy level is arbitrarily set to zero for convenience .
- the Fermi leads 3 and 4 have a much higher g-factor than the quantum dot region 2.
- the Gallium Arsenide quantum dot has a g-factor of -0.44 while the Beryllium Manganese Zinc Selenide alloy Fermi leads 3 and 4 have a g-factor in the region of 100. Accordingly, the Zeeman splitting in the Fermi leads 3 and 4 resulting from the application of the magnetic field B dc is very much greater than that in the quantum dot 2 to the extent that any electron current in the Fermi leads 3 and 4 is spin polarised with, for the orientation of the magnetic fields B dc shown in Figure 4, spin state up.
- Figures 7a and 7b show conduction band energy level diagrams corresponding to Figures 6a and 6b when B dc >0 and a spin polarised current having electron spin state up is flowing in the Fermi lead 3 as illustrated by the electron 21 in Figures 7a and 7b.
- the chemical potential ⁇ ⁇ of the input Fermi lead 3 must be comparable to or greater than the energy of the next unoccupied level of the quantum dot 2a while the chemical potential ⁇ 2 of the output Fermi lead 4 should be less than or comparable to the energy of that level namely:
- Figures 7a and 7b show conduction band level diagrams when B dc >0 and where the chemical potential ⁇ x of the input Fermi lead 3 is comparable to the energy E s of the first unoccupied singlet state on the quantum dot 2a and the chemical potential ⁇ 2 of the output Fermi lead 4 is comparable to or slightly less than the energy level E s .
- Figure 7a shows the quantum dot as having as its uppermost electron an electron 20 having spin state up
- Figure 7b shows the quantum dot 2a as having as its uppermost electron an electron 20a having spin state down which, by virtue of the Zeeman splitting, is at an energy ⁇ z higher than the energy of the electron 20 shown in Figure 7a.
- the only possible process for tunnelling of an electron in a spin-up state onto the dots in the sequential tunnelling regime is if the uppermost electron on the dot is in the spin down state. Therefore, in the Coulomb blockade regime the quantum dot 2a blocks tunnelling of spin-up state electrons 21 from the Fermi lead 3 when the uppermost electron on the quantum dot is a spin up state electron.
- This process is fundamentally different to previously introduced spin blockade effects such as described by the Wiedmann et al in Physics review letters volume 74, 1995 at page 984 because they occur for non-spin polarised currents and vanish with increasing magnetic fields, in contrast to the effect being discussed here.
- the device 1 is in the cotunnelling regime where, as explained above, tunnelling can only occur directly from one lead to the other via a virtual state on the quantum dot.
- ⁇ and K BT T are smaller than the energy level spacing on the quantum dot 2a (which is readily achieveable in the Coulomb blockade regime)
- elastic cotunnelling may occur. In this regime, the main contribution to transport through a quantum dot 2a is where the relative energy of the virtual state is minimal.
- Figures 9a and 9b are conduction band diagrams for the device 1 showing the effect of applying an electron spin resonance AC pulse B ac to the device 1 in the presence of and perpendicular to the DC magnetic field B dc .
- Figure 9a shows the quantum dot 2a as having an odd number of electrons N with the uppermost electron 20 being a spin state up electron. In this case, sequential tunnelling of a spin state up electron 21 onto the quantum dot 2a is prohibited because tunnelling into the excited triplet state level E ⁇ + at higher levels is prevented by energy conservation and tunnelling into the singlet state energy level E s is blocked by spin conservation because the Fermi leads 3 and 4 can only provide and accept electrons with spin up.
- the ratio between sequential and co-tunnelling currents can be as much as 20 to 100:1.
- Figure 10 shows a graph of current I (measured by the current sensor CS shown in Figures 1 and 2) against time (t) for the case where the AC pulse B ac is applied prior to time t 0 and at t Bac .
- a sequential tunnelling current I s is detected for a period ( ⁇ s ) equal to the spin relaxation time that is the time taken for the spin flipped electron 20" to return to its original spin state.
- the only current I c through the device is a small leakage current resulting from a cotunnelling process.
- a number of memory devices 1 embodying the invention and having, for exmaple, the structure shown in Figure 3 may be integrated on the same substrate 11 and their input and output contacts Ll and L2 and gates G coupled so as to provide a two-dimensional memory.
- Figures 11 and 12 illustrate diagrammatically one example of such a memory 30.
- Figure 11 showing a block diagram of the memory and Figure 12 part of a layout diagram for the array.
- Figure 11 shows a 3 by 3 array MA of memory devices 1. It will, however, be appreciated that, in practice, the memory array MA would generally be much larger.
- the input contact Ll of each memory device 1 in a row is coupled to a respective row conductor Rl , R2 and R3 while the output contact L2 of each memory device 1 in a column is coupled to a corresponding column conductor CI, C2, C3.
- the row conductors Rl, R2 and R3 are coupled to an input drive or shift register 100 to enable the rows to be addressed in turn by an input signal provided via an input line 101 while each of the column conductors ci, C2 and C3 is coupled via a respective sense amplifier SA1 , SA2 and SA3 to output circuitry in the form of an output shift register 102 having an output 103 from which the content of the memory can be read.
- the gate G of each memory device 1 is separately connected by a gate conductor GC to a gate drive circuit 104 that enables the gate of each memory device 1 to be individually addressed in known manner.
- the memory array MA is placed, in use, in a homogeneous DC magnetic field B dc and data is stored in the memory using a pulsed AC magnetic field B ac .
- two different gate voltages may be applied with one voltage being applied when a memory device 1 is to store a "0" and the other gate voltage being applied when the memory device is to store a "1".
- one of these gate voltages pushes the wave function of the electrons on the quantum dot 2a of that memory device into a region of higher effective g-factor so changing the Zeeman splitting for that dot.
- the frequency ⁇ of the AC magnetic field pulses B ac is selected so as to match the Zeeman splitting for only those dots to which that gate voltage has been applied. Accordingly, a Rabi spin flip will occur only for the memory devices to which that gate voltage has been applied.
- memory devices within the array are addressed by addressing the row Rl, R2, R3 containing that memory device 1 and reading the current on the column CI, C2 , C3 containing that memory device.
- memory device 1' is selected by addressing row Rl and reading column C2. If this memory device is a memory device to which the additional gate voltage has been applied, then a sequential tunnelling current I s ( Figure 10) will be detected whereas if this memory device is not a memory device to which the additional gate voltage has been applied, then only the very small cotunnelling current I c will be detected. Accordingly, an output signal representing either a "0" or "1" can be obtained for that memory device.
- the quantum dots may be formed of a III-V alloy whose composition varies from top to bottom of the dot in Figure 3.
- the quantum dot may be formed of a Gallium Indium Arsenide composition Ga ⁇ In ⁇ s where x varies from 0 to 1 throughout the depth of the quantum dot thereby causing the g-factor to vary from -0.44 when x is 0 and the material is Gallium Arsenide to +0.14 where x is 1 and the material is Indium Arsenide.
- this graded composition can readily be achieved using MBE or MOCVD techniques.
- Figure 12 shows the arrangement of the row and column conductors Rl and C2 for the memory device 1 ' and also the gate conductor GC connected to that memory device to illustrate one possible layout for the memory array MA shown in Figure 11.
- FIG. 13 shows a cross sectional view through part of a semiconductor body 10 in which the memory devices 1 are formed and illustrates one memory device
- Figure 14 shows a block diagram similar to Figure 11 for illustrating how the individual memory devices 1 are addressed.
- each memory device 1 has the same structure as shown in Figure 3. However, between the memory devices 1 and the substrate 11 is sandwiched a current grid arrangement consisting of a parallel spaced-apart first conductors 200 extending in the y direction in Figure 13 and, separated by an insulating layer 201 from the first conductors, parallel spaced- apart of second conductors 202 extending in the x direction in Figure 13 (that is into the plane of the paper) so that the first and second conductors 200 ' and 202 are mutually perpendicular.
- the second conductors 200 are separated from the memory devices 1 by an insulating layer 203.
- the insulating layer may, as is known in the art, comprise silicon dioxide or intrinsic Gallium Arsenide.
- the mutually perpendicular first and second conductors 200 and 202 are arranged such that each memory device is situated over a crossing point CP between a pair of first and second conductors 201 and 202.
- Figure 14 shows a functional block diagram of a memory embodying the invention to illustrate a driving arrangement for the memory. Again in the interest of simplicity, a three by three memory array MA' is shown. It will, however, be appreciated that the memory array will generally consist of many more memory devices 1.
- the input contacts Ll of rows of memory devices 1 are coupled via respective row conductors Rl to R3 to an input shift register 100 having an input 101 for enabling addressing of the row conductors in turn.
- each of the output contacts L2 in a column is coupled via a corresponding column conductor CI to C3 and a corresponding sense amplifier SA1 to SA3 to an output shift register 102 having an output 103.
- all of the gates G are driven at the same voltage and are coupled via a common electrode CE to the gate drive circuit (GD) 104a as is well known in the art.
- Each of the first current conductors 201 is coupled to a first drive circuit 204 while each of the second conductors 202 is coupled to a second drive circuit 205.
- the pitch of the first and second current conductors 201 and 202 is smaller than that of the row and column conductors such that each memory device 1 is uniquely associated with a pair of first and second conductors 201 and 202.
- the memory device 1 22 (where the 22 indicates that the memory device is in the second row and the second column) is coupled to the fifth first conductor 201 5 and the fifth second conductor 202 5 .
- a DC magnetic signal generator is (although not shown in Figure 14) provided to generate the DC magnetic field B dc and an AC magnetic field generator is provided to generate the AC magnetic field pulses B ac perpendicular to the DC magnetic field B dc .
- the current grid first and second drive circuits 204 and 205 are used in the same manner as the gate drive circuit 104 in Figure 11, that is to adjust locally the Zeeman splitting of a particular memory device.
- Figure 15 shows a cross sectional view similar to Figure 13 of a modification of the memory device shown in Figure 13.
- an additional element in the form of a magnetic impurity 50 such as manganese is incorporated into the quantum dot region 2 such that there is no stray magnetic field leaking into the Fermi input and output leads 3 and 4 to affect the spin polarisation of the leads.
- the additional magnetic element may be a hard magnetic layer or magnetic nanoparticles .
- the magnetic field from the additional magnetic element controls the Zeeman splitting at the quantum dot and the magnetic coercivity is such that the underlying current grid 201, 202 can be used to switch the magnetisation direction of the additional magnetic elements so as to reverse the Zeeman split energy levels (that is changing the spin down ground state into a spin up ground state or vice versa) and therefore allowing for a fully nonvolatile memory system.
- the additional magnetic element may be replaced by a layer of nuclear spin providing an Overhauser field which may be switched using standard nuclear magnetic resonance (NMR) techniques .
- NMR nuclear magnetic resonance
- each individual memory device 1 is uniquely addressed by the gate drive circuitry 104 in Figure 11 and by the first and second drive circuits 204 and 205 of Figure 14.
- a multiplexing drive scheme may be used so that a memory embodying the invention may have the layout shown in Figures 11 and 14 may be modified as shown in Figures 16 which shows a memory 32 having again a 3 by 3 array MA" of memory devices 1 connected in rows by row conductors Rl to R3 connected to input drive circuitry 100 and connected in columns CI to C3 connected via respective sense amplifiers SA1 to SA3 to output circuitry 102.
- FIG 16 further drive circuits A, B and C are provided.
- the rows of memory devices 1 are associated with conductors Bl to B3 coupled to the drive circuit B while the columns of memory devices are associated with conductors Al to A3 coupled to the drive circuit A and a common electrode CC is coupled to the drive circuit C.
- the conductors Al to A3 and Bl to B3 are connected to the gates G of the memory devices so that the voltage is provided on a conductor Al, A2 or A3 and the voltage provided on a conductor Bl, B2 and B3 is insufficient to cause the necessary Zeeman splitting while the combined voltage provided by the two conductors associated with a given memory device (for example, the conductors A2 and B2 associated with the memory device l 2 2 in Figure 16) is sufficient for the Zeeman splitting at that quantum dot 2 to allow resonance with the AC magnetic field pulses B AC to cause a Rabi spin flop.
- the drive C and the common electrode CC provide the DC magnetic field B d0 common to all of the memory devices .
- drives A and B will be equivalent to the first and second drive circuits 204 and 205 in Figure 14 and drive C will be the gate drive circuit.
- the current supplied to individual conductors Al, A2 or A3 and Bl, B2 or B3 will be insufficient to cause the necessary magnetic field to achieve the Zeeman splitting required to achieved resonance with the AC magnetic field pulses B ac and a magnetic field sufficient to cause the necessary Zeeman splitting will only be experienced by the memory device 1 at the crossover between selected conductors Al , A2 or A3 and Bl, B2 or B3, for example, the memory device 1 2,2 at the intersection of conductors A2 and B2.
- a multiplexing drive arrangement is used to both address and read the memory devices so that only one memory device is addressed or read at a time, that is only one conductor Al, A2 or A3 and only one conductor Bl, B2 or B3 is active at any one time to avoid cross talk problems between adjacent memory devices.
- the DC magnetic field B dcl applied to the Fermi input lead 3 is such that the Fermi input lead 3 is in a spin polarised state with the spin polarisation state spin state up.
- the DC magnetic field B dcr applied to the quantum dot region 2 and the Fermi output lead 4 is of the opposite polarity so that the Fermi output lead 4 is spin polarised with the spin state being down.
- Figure 17. shows schematically, a spin state up electron 23 on the Fermi input lead 3 and a spin state down electron 24 on the Fermi output lead 4 .
- the uppermost ground state electron 25 in the quantum dot 2 is a spin state up electron.
- Figure 18 shows the same conduction band energy level diagram to illustrate the effect of reversing the polarity of the DC magnetic field B dcr applied to the quantum dot 2a and the Fermi output lead 4.
- reversal of the DC magnetic field B dcr causes the uppermost electron 25a on the quantum dot 2 to adopt a spin-down state enabling a spin-up state electron 23 from the Fermi input lead 3 to tunnel onto the singlet energy level E s as shown in Figure 18.
- the Fermi outpu . lead 4 is now spin polarised with the spin state up, the electron 23 can then tunnel off the quantum dot onto the Fermi output lead 4.
- sequential tunnelling via the singlet energy level E s is now allowed and there is a finite sequential tunnelling current I ⁇ .
- Such current switches may also be used as memory devices and may be incorporated in a memory array similar to those described above with reference to Figures 14 and 16 wherein the state of each memory device is controlled by the magnetic field.
- the first and second drive circuits 204 and 205 shown in Figure 14 and the drive circuits A and B shown in Figure 16 will be used to control the polarisation of the magnetic field applied to the quantum dots 2a and output leads 4 and, as mentioned above, the AC magnetic field pulses B a ⁇ will not be required.
- each individual current switch By controlling the magnetic field applied to individual current switches using the first and second drive circuits 204 and 205 ( Figure 14) or the drive circuits A and B ( Figure 16) each individual current switch will either be capable of or not capable of passing current and one of these two states can be used to represent "0" and the other to represent "1", thereby providing a dynamic random access memory as described above.
- the memory may be made non-volatile by, as described above, incorporating an additional magnetic element into the quantum dot regions 2a and the Fermi output leads 4. It will, of course, be appreciated that the current switch described above with reference to Figures 17 and 18 may also be implemented by applying a fixed DC magnetic field to the Fermi input lead 3 and the quantum dot region 2 and switching only the field applied to the Fermi output lead 4. However, such a switch may be less effective because its operation depends now on how fast the spin state on the quantum dot 2 relaxes to its ground state.
- the quantum dot region 2 is formed of Gallium Arsenide while the Fermi input and output leads are formed of an n conductivity type Beryllium Manganese Zinc Selenide alloy.
- the memory devices described with reference to Figures 1 to 16 above may be implemented using other materials provided that the magnitude of the g-factor of the material forming the quantum dot region 2 is very much less than the magnitude of the g-factor of the material forming the Fermi input and output leads 3 and 4 and, in case of the current switch described above with reference to Figures 17 and 18, provided that the g-factor of the material forming the quantum dot region 2 is negative, the g-factor of the material forming the Fermi input and output leads 3 and 4 is positive and is very much greater than the magnitude of the g-factor of the quantum dot region.
- the memory device or current switch may be fabricated so that the dimensions of the quantum dot are about 50 nanometres which requires operation at very low temperature (typically liquid Helium temperature, that is a few Kelvin).
- very low temperature typically liquid Helium temperature, that is a few Kelvin.
- the operating temperature increases dramatically with reduction in the quantum dot size so that, for example, a scaling down of the dot size by a factor of 10 would increase the temperature required by a factor of 100 allowing room temperature operation.
- Cadmium Selenide (CdSe) nanocrystals have been fabricated with a dot diameter of 6 nanometres and a Coulomb charging energy of 30 millielectron volts.
- STM scanning tunnelling electron microscope
- a large difference in g-factor between the Fermi input and output leads 3 and 4 and the quantum dot 2a is used to ensure that the Zeeman splitting within the Fermi input and output leads 3 and 4 is considerably greater than that in the quantum dot and that the input and output leads are therefore spin polarised, in the above embodiments this is achieved by using Gallium Arsenide to form the quantum dot region 2 and an n conductivity type Beryllium Manganese Zinc Selenide alloy to form the Fermi input and output leads .
- Other magnetic semiconductor materials may be used for the Fermi input and output leads and other non-magnetic semiconductor materials may be used for forming the quantum dot region.
- the Fermi input and output leads may be formed of n conductivity type Gallium Arsenide doped with manganese while the quantum dot region may be formed of Indium Gallium Arsenide.
- the present invention provides a device where the spin state of a quantum dot can be read out or determined by sensing the current flowing through the quantum dot, which current is blocked or nearly blocked for one spin state and unblocked for the opposite spin state.
- Quantum dot having length scales of 10 to 50 nanometres can presently be fabricated using well known techniques as described in the aforementioned text book by Sohn et al . Production of a memory element having a total surface area of 50 nanometres by 50 nanometres should allow an array with memory densities of 260 Gigabits/inch 2 .
- the device may be produced in lateral configuration and on semiconducting or insulating substrates.
- addressing and read out of a memory array may be achieved using microscopic arrays of scanning tunnelling tips that are atomically sharp so that operation at a molecular or even atomic level may be possible.
- Memories embodying the present invention may be used in, for example, quantum computation and communication where manipulation of electron spin is required or may be used in conventional computing environments to, for example, replace conventional hard drives. Also, very fast switching arrays of such devices may allow very fast switching with potentially large resistance ratios of low and high power industrial machinery.
- Memory devices and switches embodying the present invention may also have applications in the area of opto- electronics enabling production of, for example, hybrid spin and optical electronic devices. Memory devices and switches embodying the present invention may also have applications in the area of tagging and tracking applications.
Abstract
Description
Claims
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AU2000270219A AU2000270219A1 (en) | 2000-08-09 | 2000-09-06 | A memory device and a memory array |
JP2002518535A JP2004523097A (en) | 2000-08-09 | 2000-09-06 | Memory device and memory array |
EP00958801A EP1328979A1 (en) | 2000-08-09 | 2000-09-06 | A memory device and a memory array |
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GBGB0019618.8A GB0019618D0 (en) | 2000-08-09 | 2000-08-09 | Spin memory device |
GB0019618.8 | 2000-08-09 |
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EP (1) | EP1328979A1 (en) |
JP (1) | JP2004523097A (en) |
AU (1) | AU2000270219A1 (en) |
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Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2002032022A2 (en) * | 2000-10-10 | 2002-04-18 | Gentech Investment Group Ag | Optical communications apparatus |
US10054400B2 (en) | 2016-09-14 | 2018-08-21 | Raytheon Company | Robot arm launching system |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5654566A (en) * | 1995-04-21 | 1997-08-05 | Johnson; Mark B. | Magnetic spin injected field effect transistor and method of operation |
US6021065A (en) * | 1996-09-06 | 2000-02-01 | Nonvolatile Electronics Incorporated | Spin dependent tunneling memory |
-
2000
- 2000-08-09 GB GBGB0019618.8A patent/GB0019618D0/en not_active Ceased
- 2000-09-06 JP JP2002518535A patent/JP2004523097A/en active Pending
- 2000-09-06 WO PCT/GB2000/003416 patent/WO2002013276A1/en not_active Application Discontinuation
- 2000-09-06 AU AU2000270219A patent/AU2000270219A1/en not_active Abandoned
- 2000-09-06 EP EP00958801A patent/EP1328979A1/en not_active Withdrawn
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5654566A (en) * | 1995-04-21 | 1997-08-05 | Johnson; Mark B. | Magnetic spin injected field effect transistor and method of operation |
US6021065A (en) * | 1996-09-06 | 2000-02-01 | Nonvolatile Electronics Incorporated | Spin dependent tunneling memory |
Non-Patent Citations (8)
Title |
---|
BANDYOPADHYAYY S: "Self-assembled nanoelectronic quantum computer based on the Rashba effect in quantum dots", PHYSICAL REVIEW B (CONDENSED MATTER), 15 MAY 2000, APS THROUGH AIP, USA, vol. 61, no. 20, pages 13813 - 13820, XP002168622, ISSN: 0163-1829 * |
CIORGA M ET AL: "Addition spectrum of a lateral dot from Coulomb and spin-blockade spectroscopy", PHYSICAL REVIEW B (CONDENSED MATTER), 15 JUNE 2000, APS THROUGH AIP, USA, vol. 61, no. 24, pages R16315 - R16318, XP002168623, ISSN: 0163-1829 * |
DIVINCENZO D P: "QUANTUM COMPUTING AND SINGLE-QUBIT MEASUREMENTS USING THE SPIN-FILTER EFFECT (INVITED)", JOURNAL OF APPLIED PHYSICS,AMERICAN INSTITUTE OF PHYSICS. NEW YORK,US, vol. 85, no. 8, PART 02A, 15 April 1999 (1999-04-15), pages 4785 - 4787, XP000823663, ISSN: 0021-8979 * |
FIEDERLING R ET AL: "INJECTION AND DETECTION OF A SPIN-POLARIZED CURRENT IN A LIGHT-EMITTING DIODE", NATURE,MACMILLAN JOURNALS LTD. LONDON,GB, vol. 402, no. 6763, 16 December 1999 (1999-12-16), pages 787 - 790, XP000960957, ISSN: 0028-0836 * |
OHNO Y ET AL: "ELECTRICAL SPIN INJECTION IN A FERROMAGNETIC SEMICONDUCTOR HETEROSTRUCTURE", NATURE,MACMILLAN JOURNALS LTD. LONDON,GB, vol. 402, no. 6763, 16 December 1999 (1999-12-16), pages 790 - 792, XP000960958, ISSN: 0028-0836 * |
RECHER ET AL.: "Quantum Dots as Spin Filter and Spin Memory", ARXIV.ORG E-PRINT ARCHIVE: COND-MAT/0003089, 6 March 2000 (2000-03-06), XP002168621 * |
RECHER ET AL.: "Quantum Dots as Spin Filter and Spin Memory", PHYSICAL REVIEW LETTERS, vol. 85, no. 9, 28 August 2000 (2000-08-28), pages 1962 - 1965 * |
SUKHORUKOV E V ET AL: "Spintronics and spin-based qubits in quantum dots", INTERNATIONAL CONFERENCE ON SEMICONDUCTOR QUANTUM DOTS (QD 2000), MUNICH, GERMANY, 31 JULY-3 AUG. 2000, vol. 224, no. 3, Physica Status Solidi B, 1 April 2001, Wiley-VCH, Germany, pages 855 - 862, XP002168624, ISSN: 0370-1972 * |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2002032022A2 (en) * | 2000-10-10 | 2002-04-18 | Gentech Investment Group Ag | Optical communications apparatus |
WO2002032022A3 (en) * | 2000-10-10 | 2003-03-20 | Gentech Invest Group Ag | Optical communications apparatus |
US10054400B2 (en) | 2016-09-14 | 2018-08-21 | Raytheon Company | Robot arm launching system |
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JP2004523097A (en) | 2004-07-29 |
AU2000270219A1 (en) | 2002-02-18 |
EP1328979A1 (en) | 2003-07-23 |
GB0019618D0 (en) | 2000-09-27 |
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