CN205723564U - Wide spectral quantum cascade Infrared Detectors - Google Patents
Wide spectral quantum cascade Infrared Detectors Download PDFInfo
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- CN205723564U CN205723564U CN201620319436.1U CN201620319436U CN205723564U CN 205723564 U CN205723564 U CN 205723564U CN 201620319436 U CN201620319436 U CN 201620319436U CN 205723564 U CN205723564 U CN 205723564U
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Abstract
This patent discloses a kind of wide spectral quantum cascade Infrared Detectors, it is by a compound semiconductor materials substrate, on substrate, eight width of alternating growth differ barrier layer and quantum well layer, and as a cycle, the MQW composition in repeated growth multiple cycle.Doing uptake zone owing to this patent have employed microstrip structure, under low temperature state, under the irradiation of infrared light, it can have broader photoresponse to compose at the quanta cascade detector that quantum well region is formed than proposing at present, thus more suitable for wide spectrographic detection application.
Description
Technical field
This patent relates to a kind of Infrared Detectors, refers specifically to a kind of multiple quantum well infrared detector and quanta cascade detector.
Background technology
In current quantum type infrared focus plane technology, photosensitive element chip is all made up of the detector pixel that the spatially electricity-optics of some guide types is discrete.Compared to mercury-cadmium tellurid detector, quantum trap infrared detector has Material growth and technical maturity, large area Array Uniformity is good, yield rate is high, the advantage of low cost, but quantum efficiency is relatively low, to such an extent as to responsiveness is relatively low, thus particularly important with the optimization of responsiveness for quantum efficiency.
The ultimate principle of quantum trap infrared detector determines the quantum efficiency of device and is proportional to absorptance, in order to improve the quantum efficiency of device, or in order to increase responsiveness under the conditions of similar detection significantly, need to increase the electron concentration in SQW ground state, but the increase of electron concentration directly increases dark current to superlinearity again, the detectivity directly resulting in device declines.The basic physics cause of the biggest dark current is to there is the highest density of electronic states that light absorbs nothing contribution at the energy position of excited state, if can effectively utilize these redundant electronic states, then the performance improvement for quantum trap infrared detector has practical value.
There has been proposed a kind of structure of quantum cascade detector at present, based on phonon assisted tunneling mechanism, there is photovoltaic property.nullSee reference document L.Gendron et.al. " Quantum cascade photodetector ",Applied Physics Letters Vol.85,Daniel Hofstetter et.al.“23GHz operation of a room temperature photovoltaic quantum cascade detector at 5.35μm”,Although the responsiveness of Applied Physics Letters Vol.89. device is superior not as good as guide type device，But operating temperature is higher，Micro-band technique can be incorporated in quanta cascade detector，Photoresponse spectrum is made to obtain broadening，It is more suitable for wide spectrographic detection application.
Summary of the invention
The purpose of this patent is to provide the Basic Mechanism of a kind of wide spectral quantum cascade Infrared Detectors, utilize micro-strip principle, the uptake zone of classical quanta cascade detector is optimized, design a kind of structurally unique quanta cascade detector, extend photoelectric absorption scope so that it is photoresponse spectrum obtains broadening.
The design of this patent is as follows:
Wide spectral quantum cascade Infrared Detectors includes substrate 1, MQW 2, upper electrode 3, bottom electrode 4.
The structure of described Infrared Detectors is GaAs or uses molecular beam epitaxy or metal organic chemical vapor deposition film growth techniques to grow lower electrode layer, the barrier layer replaced and quantum well layer, upper electrode layer successively in InP substrate 1, forms a GaAs/AlGaAs or InGaAs/InAlAs MQW 2；Electrode 3 on preparing on upper electrode layer again, lower electrode layer is prepared bottom electrode 4；
Described MQW 2 structure is:
C1L1(AL2)nC2,
C1For lower electrode layer, material identical with quantum well layer employing, Si adulterates, and concentration is 1018/cm3, thickness is that 0.5 μm is to 1 μm；C2For upper electrode layer, material identical with quantum well layer employing, Si adulterates, and concentration is 1018/cm3, thickness is that 0.1 μm is to 0.3 μm；L1For wide barrier layer, thickness is 40 to 60nm；L2Being the potential barrier sealing coat between two single cycles, thickness is 2 to 3nm；
A is single cycle, is the basic probe unit of MQW coupled structure, and its composition structure is:
QW1L1’QW2L2’QW3L3 ’QW4L4’QW5L5’QW6L6’QW7L7’QW8
Wherein: quantum well layer QW1…QW8The quantum well layer differed for width, wherein QW1And QW2It is doped, quantum well layer QW1…QW8Thickness is 2 to 8nm；Barrier layer L1’…L7' it is the barrier layer that differs of width, thickness is 3 to 6nm；L2’QW3L3’QW4L4’QW5L5’QW6L6’QW7L7’QW8Composition cascade structure；
N is periodicity, and n is 30-50 cycle；
Upper electrode 3 and bottom electrode 4 structure are three-layer metal Rotating fields: be followed successively by the AuGe layer of 100nm from bottom to top, the Ni layer of 20nm, the Au layer of 400nm, or are two layers of metal-layer structure: be followed successively by the Ti layer of 50nm from bottom to top, the Au layer of 400nm.
Upper electrode 3 is two-dimensional grating shape, and the cycle of two dimension is 2.5 μm, and hole is square, and the width of two planar dimensions is 1.5 μm, and the degree of depth in hole is 0.6 μm.
The compound semiconductor materials that detector uses is GaAs/AlGaAs or InGaAs/InAlAs system, corresponding, substrate uses GaAs or InP material, and quantum well layer uses GaAs or InGaAs material, barrier layer uses AlGaAs or InAlAs material, and upper/lower electrode layer uses GaAs or InGaAs material.
This patent has following good effect and an advantage:
1. this patent makees uptake zone owing to have employed microstrip structure, cascades detector compared to regular quantum, adds a photoelectric absorption region, and under dual photoelectric absorption machine region, photoresponse spectrum obtains effective broadening.
2. what uptake zone was prepared by this patent is thicker, it is possible to more effectively absorb incident illumination, it is possible to quantum efficiency is largely increased.
3. this patent has photovoltaic effect, and optical signal can directly change into voltage signal, and light vor signal is directly proportional to structural cycle number, and compared to photoconduction type device, this patent is easier to the accurately output realizing photosignal and reads.
Accompanying drawing explanation
For convenience of description, we are as a example by GaAs/AlGaAs mqw material, are given and illustrate that the schematic diagram of this patent is as follows:
Fig. 1 is the single cycle width spectral quantum cascade Infrared Detectors photoelectric respone schematic diagram of this patent, and rightmost side SQW is first SQW QW in next cycle1；
Fig. 2 is the wide spectral quantum cascade infrared detector structure schematic diagram of this patent；
Fig. 3 is the wide spectral quantum cascade Infrared Detectors upper electrode layer A partial enlargement cross-sectional schematic of Fig. 2.
Detailed description of the invention
Below in conjunction with the accompanying drawings the single cycle width spectral quantum cascade Infrared Detectors photoelectric respone principle of this patent is elaborated: see Fig. 1, under no-bias situation, by infrared light in doped quantum well by being in the electron excitation of ground state to excited state, form the photoelectron of detector.Owing to uptake zone is formed microstrip structure by two SQWs so that uptake zone exists the transition to excited state of the two set ground state, excited state and adjacent coupling quantum well ground state generation phonon assisted tunneling, thus photoelectron is transferred to adjacent SQW.
Apparent in order to enable to illustrate mechanism, we are with GaAs/AlGaAs quantum-well materials as embodiment.
1. the preparation of MQW chip
Example one:
(1) growth of the thin-film material of MQW chip:
Molecular number extension (MBE) is used sequentially to grow by following structure on GaAs substrate 1, C1For GaAs:Si, concentration is 1018/cm3, thickness is 0.5 μm；L1For Al0.33Ga0.67As, thickness is 40nm；QW1For GaAs:Si, concentration is 1017/cm3, thickness is 6.8nm；L1' it is Al0.33Ga0.67As, thickness is 3nm；QW2For GaAs:Si, concentration is 1017/cm3, thickness is 6.8nm；L2' it is Al0.33Ga0.67As, thickness is 5.65nm；QW3For GaAs, thickness is 2nm；L3' it is Al0.33Ga0.67As, thickness is 3.96nm；QW4For GaAs, thickness is 2.3nm；L4' it is Al0.33Ga0.67As, thickness is 3.1nm；QW5For GaAs, thickness is 2.8nm；L5' it is Al0.33Ga0.67As, thickness is 3.1nm；QW6For GaAs, thickness is 3.4nm；L6' it is Al0.33Ga0.67As, thickness is 3.1nm；QW7For GaAs, thickness is 3.8nm；L7' it is Al0.33Ga0.67As, thickness is 3.1nm；QW8For GaAs, thickness is 4.8nm；Then with QW1To QW8It is a cycle, and uses L between every two cycles2For Al0.33Ga0.67As, thickness is that 3.1nm is potential barrier isolation, 30 cycles of repeated growth, last regrowth L2For Al0.33Ga0.67As, thickness is 3.1nm； C2For GaAs:Si, concentration is 1018/cm3, thickness is 100nm, forms a MQW 2.
Width is the GaAs QW of 6.8nm1And QW2In SQW, ground state and first excited state are in SQW being formed limited localized modes, simultaneously first excited state and adjacent SQW QW3In ground state level difference less than the energy of a longitudinal optical phonon, relaxation, simultaneously SQW QW can be carried out by phonon assisted tunneling3, QW4, QW5, QW6, QW7, QW8Ground state successively all forms phonon assisted tunneling state with the ground state of adjacent quantum wells.QW in the devices1, QW2, QW3, QW4, QW5, QW6, QW7, QW8The combination of 8 quantum well structures forms a basic probe unit, i.e. forms a principle device.
(2) prepared by electrode
Upper electrode 3 is directly made in the C of top2On layer, bottom electrode 4 is by corroding part C1Material more than layer is all removed, and exposes C1Layer, then on this layer, prepare bottom electrode 4, see Fig. 2.The AuGe layer of upper/lower electrode are electronically beam evaporation 100nm, the Ni layer of 20nm, the Au layer of 400nm is prepared from.
(3) prepared by MQW chip table
At upper electrode layer C2On make grating by caustic solution, see Fig. 3, make incidence infrared luminous energy be sufficiently coupled in SQW, produce SQW QW1And QW2In electronics from ground state to first excited state transition.
Example two:
(1) growth of the thin-film material of MQW chip:
Molecular number extension (MBE) is used sequentially to grow by following structure on GaAs substrate 1, C1For GaAs:Si, concentration is 1018/cm3, thickness is 0.7 μm；L1For Al0.32Ga0.68As, thickness is 50nm；QW1For GaAs:Si, concentration is 1017/cm3, thickness is 6.9nm；L1' it is Al0.32Ga0.68As, thickness is 4nm；QW2For GaAs:Si, concentration is 1017/cm3, thickness is 6.9nm；L2' it is Al0.32Ga0.68As, thickness is 5.8nm；QW3For GaAs, thickness is 2.2nm；L3' it is Al0.32Ga0.68As, thickness is 4.1nm； QW4For GaAs, thickness is 2.5nm；L4' it is Al0.32Ga0.68As, thickness is 3.3nm；QW5For GaAs, thickness is 3nm；L5' it is Al0.32Ga0.68As, thickness is 3.3nm；QW6For GaAs, thickness is 3.5nm；L6' it is Al0.32Ga0.68As, thickness is 3.3nm；QW7For GaAs, thickness is 4.2nm；L7' it is Al0.32Ga0.68As, thickness is 3.3nm；QW8For GaAs, thickness is 5.2nm；Then with QW1To QW8It is a cycle, and uses L between every two cycles2For Al0.32Ga0.68As, thickness is that 2.5nm is potential barrier isolation, 40 cycles of repeated growth, last regrowth L2For Al0.32Ga0.68As, thickness is 2.5nm；C2For GaAs:Si, concentration is 1018/cm3, thickness is 200nm, forms a MQW 2.
Width is the GaAs QW of 6.9nm1And QW2In SQW, ground state and first excited state are in SQW being formed limited localized modes, simultaneously first excited state and adjacent SQW QW3In ground state level difference less than the energy of a longitudinal optical phonon, relaxation, simultaneously SQW QW can be carried out by phonon assisted tunneling3, QW4, QW5, QW6, QW7, QW8Ground state successively all forms phonon assisted tunneling state with the ground state of adjacent quantum wells.QW in the devices1, QW2, QW3, QW4, QW5, QW6, QW7, QW8The combination of 8 quantum well structures forms a basic probe unit, i.e. forms a principle device.
(2) prepared by electrode
Upper electrode 3 is directly made in the C of top2On layer, bottom electrode 4 is by corroding part C1Material more than layer is all removed, and exposes C1Layer, then on this layer, prepare bottom electrode 4, see Fig. 2.The AuGe layer of upper/lower electrode are electronically beam evaporation 100nm, the Ni layer of 20nm, the Au layer of 400nm is prepared from.
(3) prepared by MQW chip table
At upper electrode layer C2On make grating by caustic solution, see Fig. 3, make incidence infrared luminous energy be sufficiently coupled in SQW, produce SQW QW1And QW2In electronics from ground state to first excited state transition.
Example three:
(1) growth of the thin-film material of MQW chip:
Molecular number extension (MBE) is used sequentially to grow by following structure on GaAs substrate 1, C1For GaAs:Si, concentration is 1018/cm3, thickness is 1 μm；L1For Al0.31Ga0.69As, thickness is 60nm；QW1For GaAs:Si, concentration is 1017/cm3, thickness is 7nm；L1' it is Al0.31Ga0.69As, thickness is 3.5nm；QW2For GaAs:Si, concentration is 1017/cm3, thickness is 7nm；L2' it is Al0.31Ga0.69As, thickness is 6nm；QW3For GaAs, thickness is 2.4nm；L3' it is Al0.31Ga0.69As, thickness is 4.3nm；QW4For GaAs, thickness is 2.7nm；L4' it is Al0.31Ga0.69As, thickness is 3.5nm；QW5For GaAs, thickness is 3.2nm；L5' it is Al0.31Ga0.69As, thickness is 3.5nm；QW6For GaAs, thickness is 3.7nm；L6' it is Al0.31Ga0.69As, thickness is 3.5nm；QW7For GaAs, thickness is 4.4nm；L7' it is Al0.31Ga0.69As, thickness is 3.5nm；QW8For GaAs, thickness is 5.4nm；Then with QW1To QW8It is a cycle, and uses L between every two cycles2For Al0.31Ga0.69As, thickness is that 3nm is potential barrier isolation, 50 cycles of repeated growth, last regrowth L2For Al0.31Ga0.69As, thickness is 3nm；C2For GaAs:Si, concentration is 1018/cm3, thickness is 300nm, forms a MQW 2.
Width is the GaAs QW of 7nm1And QW2In SQW, ground state and first excited state are in SQW being formed limited localized modes, simultaneously first excited state and adjacent SQW QW3In ground state level difference less than the energy of a longitudinal optical phonon, relaxation, simultaneously SQW QW can be carried out by phonon assisted tunneling3, QW4, QW5, QW6, QW7, QW8Ground state successively all forms phonon assisted tunneling state with the ground state of adjacent quantum wells.QW in the devices1, QW2, QW3, QW4, QW5, QW6, QW7, QW8The combination of 8 quantum well structures forms a basic probe unit, i.e. forms a principle device.
(2) prepared by electrode
Upper electrode 3 is directly made in the C of top2On layer, bottom electrode 4 is by corroding part C1Material more than layer is all removed, and exposes C1Layer, then on this layer, prepare bottom electrode 4, see Fig. 2.The AuGe layer of upper/lower electrode are electronically beam evaporation 100nm, the Ni layer of 20nm, the Au layer of 400nm is prepared from.
(3) prepared by MQW chip table
At upper electrode layer C2On make grating by caustic solution, see Fig. 3, make incidence infrared luminous energy be sufficiently coupled in SQW, produce SQW QW1And QW2In electronics from ground state to first excited state transition.
2. the work process of device:
MQW chip is placed in a refrigeration dewar with infrared band optical window.Infrared response wave band is 8-10 micron, and chip freezes to about 80K.Bias voltage 7 is set to 0V, forms short-circuit condition, subsequently infrared light 5 is radiated on MQW chip, now causes SQW QW due to exciting of infrared light1And QW2In electronics be excited to enter that first excited state, first excited state and adjacent coupling quantum well ground state generation phonon assisted tunneling, thus photoelectron is transferred to adjacent SQW, and this electronics are very difficult is reversely transported to QW1And QW2In SQW.The completing of this process is the formation of photo-signal 6.Cascade detector relative to regular quantum, This structure increases a photoelectric absorption region, enhance device quantum efficiencies, and broadening photoresponse spectrum.
Claims (2)
1. a wide spectral quantum cascade Infrared Detectors, including substrate (1), MQW (2), upper electrode (3), bottom electrode (4), it is characterised in that:
The structure of described Infrared Detectors is GaAs or InP substrate (1) is upper uses molecular beam epitaxy or metal organic chemical vapor deposition film growth techniques to grow lower electrode layer, the barrier layer replaced and quantum well layer, upper electrode layer successively, forms a GaAs/AlGaAs or InGaAs/InAlAs MQW (2)；Electrode (3) on preparing on upper electrode layer, lower electrode layer is prepared bottom electrode (4)；
Described MQW (2) structure is:
C1L1(AL2)nC2,
C1For lower electrode layer, thickness is that 0.5 μm is to 1 μm；C2For upper electrode layer, thickness is that 0.1 μm is to 0.3 μm；L1For wide barrier layer, thickness is 40 to 60nm；L2Being the potential barrier sealing coat between two single cycles, thickness is 2 to 3nm；
A is single cycle, is the basic probe unit of MQW coupled structure, and its composition structure is:
QW1L1’QW2L2’QW3L3 ’QW4L4’QW5L5’QW6L6’QW7L7’QW8
Wherein: quantum well layer QW1…QW8The quantum well layer differed for width, wherein QW1And QW2It is doped, quantum well layer QW1…QW8Thickness is 2 to 8nm；Barrier layer L1’…L7' it is the barrier layer that differs of width, thickness is 3 to 6nm；L2’QW3L3’QW4L4’QW5L5’QW6L6’QW7L7’QW8Composition cascade structure；
N is periodicity, and n is 30-50 cycle；
Upper electrode (3) and bottom electrode (4) structure are three-layer metal Rotating fields: be followed successively by the AuGe layer of 100nm from bottom to top, the Ni layer of 20nm, the Au layer of 400nm；Or it is two layers of metal-layer structure: be followed successively by the Ti layer of 50nm from bottom to top, the Au layer of 400nm.
A kind of wide spectral quantum cascade Infrared Detectors the most according to claim 1, it is characterized in that: described upper electrode (3) is two-dimensional grating shape, the cycle of two dimension is 2.5 μm, hole is square, the width of two planar dimensions is 1.5 μm, and the degree of depth in hole is 0.6 μm.
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| CN112635615A (en) * | 2020-11-26 | 2021-04-09 | 中国工程物理研究院电子工程研究所 | Photovoltaic type nitride sub-band transition infrared detector with multi-absorption quantum well |
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