CN118099257B - Dual-color infrared detector and preparation method thereof - Google Patents
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Abstract
The invention provides a double-color infrared detector which can be applied to the technical field of semiconductor optoelectronic devices. The infrared detector includes: a substrate; a buffer layer positioned on the surface of the substrate; the bottom contact layer is positioned on one side of the buffer layer away from the substrate; the first absorption layer is positioned on one side of the bottom contact layer away from the substrate; the second absorption layer is positioned on one side of the first absorption layer away from the substrate; a barrier layer positioned on one side of the second absorption layer away from the substrate; a top contact layer located on a side of the barrier layer away from the substrate; and a cap layer on a side of the top contact layer remote from the substrate. The bottom contact layer, the first absorption layer, the second absorption layer, the barrier layer and the top contact layer are all of M-type superlattice structures; the periods of the M-type superlattice structures of the first absorption layer and the second absorption layer are different, and the absorption coefficient of the detector can be adjusted by changing the thickness ratio of the first absorption layer and the second absorption layer. The invention also provides a preparation method of the double-color infrared detector.
Description
Technical Field
The invention relates to the technical field of semiconductor optoelectronic devices, in particular to a bicolor infrared detector and a preparation method thereof.
Background
In the infrared imaging field, each wave band has the imaging advantages and applications, the mid-wave infrared (MWIR) wave band corresponds to the wave band of 3-5 μm, the long-wave infrared (LWIR) wave band corresponds to the wave band of 8-14 μm, and the very-long-wave infrared (VLWIR) wave band corresponds to the wave band of more than 14 μm. Both MWIR and LWIR can be used for thermal imaging, but are better in terms of contrast of the image, detector sensitivity and light transmittance, and are better in terms of radiance. VLWIR are more useful for spatial light imaging.
Infrared detectors are commonly used in particular for detection of substances, monitoring of high-temperature industrial processes, fire monitoring, and research of atmospheric science, such as gas leakage detection and chemical substance identification; and key temperature data can be provided for monitoring high-temperature industrial processes such as steelmaking, metallurgy and the like. The most commonly used tellurium-cadmium-mercury infrared detector in the market has poor uniformity and stability of the material, high Auger recombination rate and device performance reaching the bottleneck. In contrast, the superlattice infrared detector has obvious advantages, auger recombination can be inhibited for M-type superlattice (M-superlattice, M-SL) materials by regulating and controlling the energy band structure, and the effective mass of carriers is relatively large due to the special energy band structure, so that the inhibiting effect on tunneling current is also achieved. In addition, the existing dual-band detection is to stack materials with different absorption bands together, or to use a very complex dual-mesa three-electrode structure, or to use a back-to-back (back-to-back) structure to perform dual-color detection. The process is very complex, and multiple etching can cause damage to the device. Lattice mismatch of materials can also lead to poor uniformity of the film, while superlattice growth by molecular beam epitaxy can minimize lattice mismatch problems. Most importantly, the absorption coefficient of dual-band detectors of these structures is not controllable and cannot be designed as desired.
Disclosure of Invention
First, the technical problem to be solved
In order to solve at least one of the above technical problems of the dual-color infrared detector in the prior art, the embodiment of the invention provides a dual-color infrared detector, and the functional layers of the detector are all made of M-type superlattice materials, so that lattice mismatch is reduced. Detection of different wavebands can be achieved by changing the materials of the first absorption layer, the second absorption layer, the top contact layer and the bottom contact layer of the device, and the absorption coefficient of the detector can be adjusted by changing the thickness ratio of the first absorption layer to the second absorption layer.
(II) technical scheme
Aiming at the technical problems, the embodiment of the invention provides a bicolor infrared detector and a preparation method thereof.
According to a first aspect of the present invention there is provided a bi-colour infrared detector comprising: a substrate, the material of the substrate comprising gallium antimonide material; a buffer layer positioned on the surface of the substrate; the bottom contact layer is positioned on one side of the buffer layer away from the substrate; the first absorption layer is positioned on one side of the bottom contact layer away from the substrate; the second absorption layer is positioned on one side of the first absorption layer away from the substrate; a barrier layer positioned on one side of the second absorption layer away from the substrate; a top contact layer located on a side of the barrier layer away from the substrate; and a cap layer on a side of the top contact layer remote from the substrate. The bottom contact layer, the first absorption layer, the second absorption layer, the barrier layer and the top contact layer are all M-shaped superlattice structures composed of indium arsenide, gallium antimonide, aluminum antimonide and gallium antimonide; the buffer layer, the bottom contact layer, the first absorption layer, the second absorption layer, the barrier layer, the top contact layer and the cover layer are grown in a molecular beam epitaxy mode; and the periods of the M-type superlattice structures of the first absorption layer and the second absorption layer are different, so that the forbidden bandwidth of the first absorption layer is smaller than that of the second absorption layer, and the cut-off wavelength of the light detection of the first absorption layer is larger than that of the light detection of the second absorption layer.
In some exemplary embodiments, the bottom contact layer has the same thickness ratio of indium arsenide, gallium antimonide, aluminum antimonide, and gallium antimonide in a single period of the M-superlattice structure of the first absorber layer; and/or the thickness ratio of each layer of indium arsenide, gallium antimonide, aluminum antimonide and gallium antimonide in a single period of the M-type superlattice structure of the top contact layer and the second absorption layer is the same; and/or the monolayer thickness of indium arsenide in the barrier layer material is less than the monolayer thickness of indium arsenide in the first absorber layer and the second absorber layer.
In some exemplary embodiments, the first absorber layer is doped n-type with a doping concentration of 5 x 10 15-5×1016cm-3; and/or the doping type of the second absorption layer is n-type or p-type doping, the doping type is determined by the detected wave band, and the doping concentration is 5×10 15-5×1016cm-3.
In some exemplary embodiments, the barrier layer is unintentionally doped, exhibiting a p-type doping, at a concentration of 1 x 10 15-1×1016cm-3; and/or the cutoff wavelength of the superlattice material of the barrier layer corresponds to a mid-wave infrared band; and/or the conduction band vacuum energy level of the barrier layer is higher than the conduction band vacuum energy levels of the first absorption layer and the second absorption layer; and/or the difference between the valence band vacuum energy level of the barrier layer and the valence band vacuum energy levels of the first absorption layer and the second absorption layer is less than 0.01eV; and/or the band gap of the barrier layer is higher than that of the first absorption layer and the second absorption layer.
In some exemplary embodiments, the substrate material comprises tellurium-doped n-type gallium antimonide, the tellurium doping concentration being 1×10 17-1×1018cm-3; and/or the buffer layer material comprises tellurium-doped n-type gallium antimonide, and the tellurium doping concentration is 1×10 17-1×1018cm-3.
In some exemplary embodiments, the dual-color infrared detector further comprises: a first electrode located on one side of the bottom contact layer away from the substrate and on the outer side of the first absorption layer; a second electrode located on a side of the cap layer away from the substrate; and a passivation layer on the outer surfaces of the first absorption layer, the second absorption layer, the barrier layer, the top contact layer and the cap layer and on one side of the bottom contact layer away from the substrate, wherein the passivation layer is disconnected at the first electrode and the second electrode.
In some exemplary embodiments, the bottom contact layer is doped n-type with a doping concentration of 1 x 10 17-1×1018cm-3, the bottom contact layer forming an ohmic contact with the first electrode; and/or the material of the cover layer comprises n-type doped indium arsenide, the doping concentration is 1×10 17-1×1018cm-3, and the cover layer forms ohmic contact with the second electrode.
In some exemplary embodiments, the dual-color infrared detector includes at least one of the following features: the sum of the thicknesses of the first absorption layer and the second absorption layer is less than or equal to 4 mu m; the thickness of the top contact layer is less than or equal to 1 mu m; the thickness of the bottom contact layer is less than or equal to 1 mu m; the thickness of the barrier layer is 1 μm or less.
The second aspect of the invention provides a method for preparing a bicolor infrared detector, which comprises the following steps: and (3) epitaxial layer growth: sequentially epitaxially growing a buffer layer, a bottom contact layer, a first absorption layer, a second absorption layer, a barrier layer, a top contact layer and a cover layer on a substrate to obtain a sample containing an epitaxial layer; etching: transferring the etched pattern to a sample containing an epitaxial layer through photoetching, exposure and development processes, and then etching to a bottom contact layer; preparing an ohmic contact electrode: transferring the pattern of the electrode to the sample by photolithography, exposure and development processes; passivation: transferring the pattern of the passivation layer onto the sample by photolithography, exposure and development processes, and growing a passivation layer material on the mesa structure, wherein the materials of the substrate and the buffer layer include gallium antimonide material; the bottom contact layer, the first absorption layer, the second absorption layer, the barrier layer and the top contact layer are all M-shaped superlattice structures composed of indium arsenide, gallium antimonide, aluminum antimonide and gallium antimonide; the periods of the M-type superlattice structures of the first absorption layer and the second absorption layer are different, the forbidden bandwidth of the first absorption layer is smaller than that of the second absorption layer, and further the cut-off wavelength of the light detection of the first absorption layer is larger than that of the light detection of the second absorption layer.
In some exemplary embodiments, epitaxial layer growth is performed in a molecular beam epitaxy apparatus.
(III) beneficial effects
According to the technical scheme, the double-color infrared detector and the preparation method thereof have at least one of the following beneficial effects:
(1) The band gap, conduction band and valence band vacuum energy level positions of the superlattice can be regulated and controlled by adjusting parameters such as thicknesses of different components in the superlattice period.
(2) By adjusting the thickness ratio of the first absorption layer and the second absorption layer, the absorption coefficient of the bicolor infrared detector can be adjusted.
Drawings
Fig. 1 schematically shows a schematic structure of a two-color infrared detector according to an embodiment of the present invention.
Fig. 2 schematically shows a flow chart of a method for manufacturing a bicolor infrared detector according to an embodiment of the invention.
Fig. 3 schematically shows a subband dispersion map of a two-color infrared detector at 0V bias with an M-type superlattice as an absorption layer with different period numbers of layers according to an embodiment of the present invention, wherein (a) in fig. 3 schematically shows a subband dispersion map absorption layer of a two-color infrared detector at 0V bias with an M-type superlattice of 6/4/1/4MLs as an absorption layer according to an embodiment of the present invention; fig. 3 (b) schematically shows a sub-band dispersion map absorption layer of a bicolor infrared detector with an 11/4/1/4MLs M-type superlattice as an absorption layer at 0V bias according to an embodiment of the present invention; FIG. 3 (c) schematically illustrates a sub-band dispersion map absorber layer at 0V bias for a two-color infrared detector with a 12/4/1/4MLs M-type superlattice as the absorber layer according to an embodiment of the invention; fig. 3 (d) schematically illustrates a sub-band dispersion map absorption layer of a dual-color infrared detector with a 14/4/1/4MLs M-type superlattice as the absorption layer according to an embodiment of the present invention, where ML (monolayer) is a layer number unit, one ML represents a thickness of one-time lattice constant, and lattice constants of indium arsenide (InAs), gallium antimonide (GaSb), aluminum antimonide (AlSb) are substantially equal, about equal to 0.6nm, for example, 6 in M-SL of 6/4/1/4MLs, and the thickness of the represented monocycle superlattice is 6 times lattice constant of InAs.
Fig. 4 schematically shows a sub-band dispersion diagram of a dichroic infrared detector with an M-type superlattice of 12/4/1/4MLs as a barrier layer at a 0V bias according to an embodiment of the invention.
Fig. 5 schematically shows a graph of absorption coefficient of a two-color infrared detector having M-type superlattices of different InAs thicknesses as absorption layers according to an embodiment of the invention, in which (a) in fig. 5 schematically shows a graph of absorption coefficient of a two-color infrared detector having an M-type superlattice of 6/4/1/4MLs as an absorption layer according to an embodiment of the invention; fig. 5 (b) schematically shows a graph of absorption coefficient of a two-color infrared detector having an M-type superlattice of 11/4/1/4MLs as an absorption layer according to an embodiment of the present invention, as a function of wavelength; fig. 5 (c) schematically shows a graph of absorption coefficient of a bicolor infrared detector having an M-type superlattice of 12/4/1/4MLs as an absorption layer according to an embodiment of the present invention, as a function of wavelength; fig. 5 (d) schematically shows the absorption coefficient versus wavelength curve of a bicolor infrared detector having an M-type superlattice of 14/4/1/4MLs as an absorption layer according to an embodiment of the present invention.
Fig. 6 schematically shows a graph of absorption coefficient versus wavelength for a dual-color infrared detector of different thickness ratios of a first absorption layer and a second absorption layer according to an embodiment of the present invention, wherein (a) in fig. 6 schematically shows a graph of absorption coefficient versus wavelength for a mid-long wavelength dual-color detector of different thickness ratios of a first absorption layer and a second absorption layer according to an embodiment of the present invention at 77K; fig. 6 (b) schematically shows the absorption coefficient versus wavelength for a long-long wavelength dual-color detector with different thickness ratios of the first and second absorption layers according to an embodiment of the present invention at 77K; fig. 6 (c) schematically shows the absorption coefficient versus wavelength for a long-very long wavelength bicolor detector with different thickness ratios of the first absorption layer and the second absorption layer according to an embodiment of the present invention at 77K.
FIG. 7 schematically illustrates energy band structure curves of a mid-long wave dual-color infrared detector under different bias voltages according to an embodiment of the present invention, wherein (a) in FIG. 7 schematically illustrates energy band structure curves of a mid-long wave dual-color infrared detector under a bias voltage of 0V according to an embodiment of the present invention; fig. 7 (b) schematically shows an energy band structure curve of the mid-long wave bicolor infrared detector at-0.2V bias according to an embodiment of the present invention.
FIG. 8 schematically shows energy band structure curves of a long-long wave two-color infrared detector under different bias voltages according to an embodiment of the present invention, wherein (a) in FIG. 8 schematically shows energy band structure curves of a long-long wave two-color infrared detector under a bias voltage of 0V according to an embodiment of the present invention; fig. 8 (b) schematically shows an energy band structure curve of a long-long wave bicolor infrared detector under-0.2V bias according to an embodiment of the present invention.
FIG. 9 schematically illustrates energy band structure curves of a long-very long wave bicolor infrared detector under different bias voltages according to an embodiment of the present invention, wherein (a) in FIG. 9 schematically illustrates energy band structure curves of a long-very long wave bicolor infrared detector under a bias voltage of 0V according to an embodiment of the present invention; fig. 9 (b) schematically shows an energy band structure curve of the long-very long wave bicolor infrared detector at-0.2V bias according to an embodiment of the present invention.
Reference numerals illustrate:
1-a substrate; 2-a buffer layer; 3-a bottom contact layer; 4-a first absorbent layer; 5-a second absorbent layer; a 6-barrier layer; 7-a top contact layer; 8-cap layer; 9-a passivation layer; 10-a first electrode; 11-a second electrode.
Detailed Description
The present invention will be further described in detail below with reference to specific embodiments and with reference to the accompanying drawings, in order to make the objects, technical solutions and advantages of the present invention more apparent. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Currently, bulk materials (such as gallium aluminum antimonide and gallium aluminum arsenide) are mostly adopted as barrier layers in mainstream barrier detectors, however, lattice mismatch can be generated between the bulk materials and type II superlattice materials serving as absorption layers, and the performance of devices can be influenced.
In the invention, the same superlattice structure is adopted as the absorption layer and the barrier layer, meanwhile, the semiconductor materials forming the superlattice are 6.1A, so that lattice mismatch is reduced to the greatest extent, and meanwhile, the superlattice structure can control and regulate the size of a band gap and the absorption coefficient through energy band engineering so as to obtain a structure more meeting requirements.
The key to the design of the barrier detector used in the present invention is to make the valence band offset (valence band offset, VBO) of the barrier layer 6 from the absorber layer as small as possible, and a larger VBO will create an electric field in the absorber layer adjacent to the barrier layer, thereby forming a depletion region and contributing to the recombination (GR) current. The thickness of the indium arsenide layer in the M-type superlattice structure (indium arsenide, gallium antimonide, aluminum antimonide and gallium antimonide) is adjusted, the change of the cut-off wavelength of the absorption layer is realized under the condition that VBO is ensured to be as small as possible, the absorption layers are overlapped, and then the double-color infrared detector from 2 mu M to 20 mu M can be designed, and the absorption coefficient is adjustable by adjusting the thickness of the two absorption layers.
Fig. 1 schematically shows a schematic structure of a two-color infrared detector according to an embodiment of the present invention.
As shown in fig. 1, a dual-color infrared detector according to an embodiment of the present invention includes: a substrate 1, the material of the substrate 1 comprising gallium antimonide material; a buffer layer 2 located on the surface of the substrate 1; a bottom contact layer 3 located on a side of the buffer layer 2 away from the substrate 1; a first absorption layer 4 located on a side of the bottom contact layer 3 remote from the substrate 1; a second absorption layer 5 located on a side of the first absorption layer 4 remote from the substrate 1; a barrier layer 6 located on a side of the second absorption layer 5 remote from the substrate 1; a top contact layer 7 located on a side of the barrier layer 6 remote from the substrate 1; and a cap layer 8 on the side of the top contact layer 7 remote from the substrate 1.
In the present embodiment, the bottom contact layer 3, the first absorption layer 4, the second absorption layer 5, the barrier layer 6, and the top contact layer 7 are all M-type superlattice structures composed of indium arsenide, gallium antimonide, aluminum antimonide, and gallium antimonide (in which indium arsenide, gallium antimonide, aluminum antimonide, and gallium antimonide are expressed as InAs/GaSb/AlSb/GaSb); the buffer layer 2, the bottom contact layer 3, the first absorption layer 4, the second absorption layer 5, the barrier layer 6 and the top contact layer 7 are grown by a molecular beam epitaxy mode; and the periods of the M-type superlattice structures of the first absorption layer 4 and the second absorption layer 5 are different, so that the forbidden bandwidth of the first absorption layer 4 is smaller than that of the second absorption layer 5, and further the cut-off wavelength of the light detection of the first absorption layer 4 is larger than that of the light detection of the second absorption layer 5.
In some exemplary embodiments, the substrate 1 and the buffer layer 2 are both tellurium (Te) -doped n-type gallium antimonide (GaSb) materials with a doping concentration of 1×10 17-1×1018cm-3. The lattice mismatch problem during material growth is minimized by introducing the buffer layer 2.
In some exemplary embodiments, the dual-color infrared detector further comprises: a first electrode 10 located on a side of the bottom contact layer 3 remote from the substrate 1 and on an outer side of the first absorption layer 4; a second electrode 11 located on a side of the cap layer 8 remote from the substrate 1; and a passivation layer 9 on the outer surfaces of the first absorption layer 4, the second absorption layer 5, the barrier layer 6, the top contact layer 7 and the cap layer 8, and on the side of the bottom contact layer 3 remote from the substrate 1, and the passivation layer 9 is disconnected at the first electrode 10 and the second electrode 11.
In some exemplary embodiments, the bottom contact layer 3 and the first absorption layer 4 are made of the same material, and the top contact layer 7 and the second absorption layer 5 are made of the same material, i.e. the thickness ratio of layers of indium arsenide, gallium antimonide, aluminum antimonide and gallium antimonide (InAs/GaSb/AlSb/GaSb) in a single period of the super-M superlattice structure is the same. The material of the barrier layer 6 is also an M-type superlattice composed of indium arsenide, gallium antimonide, aluminum antimonide and gallium antimonide (InAs/GaSb/AlSb/GaSb), and differs from the material of the first absorber layer 4 and the second absorber layer 5 in that the thickness of the indium arsenide (InAs) layer in the barrier layer 6 is smaller than the thickness of the indium arsenide (InAs) layer in the first absorber layer 4 and the second absorber layer 5 in a single period of the M-type superlattice structure, thereby resulting in a higher conduction band vacuum level and substantially the same valence band vacuum level. The cap layer 8 is an n-doped indium arsenide (InAs) bulk material. Except the gallium antimonide (GaSb) substrate 1 layer, each layer is grown in a molecular beam epitaxy mode.
According to the superlattice energy band engineering theory, the band gap, conduction band and valence band vacuum energy level positions of the superlattice can be regulated and controlled by adjusting parameters such as thicknesses of different components in the superlattice period.
According to the beer lambert law, the absorption coefficient can be adjusted by adjusting the thickness ratio of the first absorption layer 4 and the second absorption layer 5.
In some exemplary embodiments, an antimonide-based two-color infrared detector with an M-superlattice (M-SL) having an adjustable absorption coefficient, the first absorber layer 4 of the medium-long wavelength two-color infrared detector employs an M-SL (ML is a layer number unit, one ML represents a thickness of one lattice constant, and the lattice constant of InAs, gaSb, alSb is substantially equal, about equal to 0.6 nm) having an InAs/GaSb/AlSb/GaSb layer number period of 6/4/1/MLs (representing the layer number of various materials in a single period), and the second absorber layer 5 employs an M-SL having an InAs/GaSb/AlSb/GaSb layer number period of 11/4/1/4MLs, and the thickness ratio of the first absorber layer 4 to the second absorber layer 5 is 1: and 5, ensuring that the peak values of absorption coefficients of the medium-long wave double-color detection are basically equal. The first absorption layer 4 of the long-long wave bicolor infrared detector adopts M-SL with the layer number period of InAs/GaSb/AlSb/GaSb of 11/4/1/4MLs, the second absorption layer 5 adopts M-SL with the layer number period of InAs/GaSb/AlSb/GaSb of 12/4/1/4MLs, and the thickness ratio of the first absorption layer 4 to the second absorption layer 5 is 1: and 4, ensuring that the peak values of absorption coefficients of the long-long wave double-color detection are basically equal. The first absorption layer 4 of the long-very long wave double-color infrared detector adopts M-SL with the layer number period of InAs/GaSb/AlSb/GaSb of 11/4/1/4MLs, the second absorption layer 5 adopts M-SL with the layer number period of InAs/GaSb/AlSb/GaSb of 14/4/1/4MLs, and the thickness ratio of the first absorption layer 4 to the second absorption layer 5 is 1:2, ensuring that the peak values of absorption coefficients of long-very long wave bicolor detection are basically equal. It should be noted that the ratio of the thicknesses of the first absorption layer 4 and the second absorption layer 5 is not limited to the above-mentioned cases, and may be adjusted according to the actual situation for the purpose of realizing the two-color infrared detection, and it is not necessary that the peak values of the absorption coefficients are substantially equal. The sum of the thicknesses of the first absorption layer 4 and the second absorption layer 5 is 4 μm or less. The absorption coefficient change curves of the bicolor infrared detectors with different thickness ratios of the first absorption layer 4 and the second absorption layer 5 of the three detectors with the wavelength at 77K are shown in fig. 6.
In some exemplary embodiments, the doping type of the first absorption layer 4 is n-type doping with a doping concentration of 5×10 15-5×1016cm-3; the doping type of the second absorption layer 5 is n-type or p-type doping, the doping type is determined by the detected wave band, and for the medium-long wave double-color infrared detector, the second absorption layer 5 (namely the corresponding medium wave detected material) is set to be p-type weak doping, and the concentration is 5 multiplied by 10 15-5×1016cm-3; the ratio of the thickness of the first absorption layer 4 and the thickness of the second absorption layer 5 ensures that the peaks of the absorption coefficients detected by the first absorption layer 4 and the second absorption layer 5 are substantially equal (differ by less than 20%).
The superlattice structure design of the regulation absorption region (comprising the first absorption layer 4 and the second absorption layer 5) and the barrier region (comprising the barrier layer 6) is calculated by using eight-band perturbation model theory and a Latin-Cohn (Luttinger-Kohn) model through energy band engineering, so that the vacuum energy level of the conduction band of the barrier region is higher than that of the absorption region and is about 0.1-0.2eV, the difference between the vacuum energy level of the valence band of the barrier region and the vacuum energy level of the valence band of the absorption region is controlled to be within 0.01eV, and the band gap of the barrier region is 0.2eV or more higher than that of the absorption region for detecting long-very long waves, thereby realizing the effect of blocking most electrons.
In some exemplary embodiments, the bottom contact layer 3, the first absorption layer 4, the second absorption layer 5, the barrier layer 6, and the top contact layer 7 are each composed of a group iii-v antimonide semiconductor, each composed of a InAs, gaSb, alSb-based superlattice, and the first absorption layer 4 has a smaller forbidden bandwidth than the second absorption layer 5, i.e., the first absorption layer 4 has a larger cut-off wavelength for light detection than the second absorption layer 5. The total thickness of the two absorption layers is controlled within 4 micrometers, the superlattice material of the bottom contact layer 3 is the same as that of the first absorption layer 4, the superlattice material of the top contact layer 7 is the same as that of the second absorption layer 5, the thicknesses of the bottom contact layer 3 and the top contact layer 7 are both less than or equal to 1 micrometer, the cutoff wavelength of the superlattice material of the barrier layer 6 is a medium wave infrared band, and the thickness of the barrier layer 6 is less than or equal to 1 micrometer. The bottom contact layer 3, the top contact layer 7 and the cap layer 8 are heavily doped n-type with a doping concentration of 1 x10 17-1×1018cm-3 in order to facilitate ohmic contact with the metal electrode, wherein the bottom contact layer 3 forms an ohmic contact with the first electrode 10 and the cap layer 8 forms an ohmic contact with the second electrode 11.
In some exemplary embodiments, the barrier layer 6 is unintentionally doped, exhibiting a weak p-type doping, at a concentration of 1×10 15-1×1016cm-3.
Fig. 2 schematically shows a flow chart of a method for manufacturing a bicolor infrared detector according to an embodiment of the invention.
Referring to fig. 2, the method for manufacturing the dual-color infrared detector according to the embodiment of the invention includes steps S110 to S140.
In step S110, epitaxial layer growth: a buffer layer 2, a bottom contact layer 3, a first absorption layer 4, a second absorption layer 5, a barrier layer 6, a top contact layer 7 and a cap layer 8 are epitaxially grown in this order on a substrate 1 to obtain a sample containing an epitaxial layer. This step is performed in a molecular beam epitaxy apparatus.
In some exemplary embodiments, the materials of the substrate 1 and the buffer layer 2 include gallium antimonide material, the bottom contact layer 3, the first absorption layer 4, the second absorption layer 5, the barrier layer 6, and the top contact layer 7 are all M-type superlattice structures composed of indium arsenide, gallium antimonide, aluminum antimonide, and gallium antimonide, periods of the M-type superlattice structures of the first absorption layer 4 and the second absorption layer 5 are different, and a forbidden band width of the first absorption layer 4 is smaller than a forbidden band width of the second absorption layer 5, so that a cut-off wavelength of light detection of the first absorption layer 4 is longer than a cut-off wavelength of light detection of the second absorption layer 5.
For example, a Te-doped n-type GaSb buffer layer 2, a bottom contact layer 3 of an n-type doped M-type superlattice material, a first absorption layer 4 of a weak n-type doped M-type superlattice, a second absorption layer 5 of a weak n-type or weak p-type doped M-type superlattice, a barrier layer 6 of a weak p-type doped M-type superlattice, a top contact layer 7 of an n-type heavily doped indium arsenide, gallium antimonide, aluminum antimonide and gallium antimonide superlattice material, and a cap layer 8 of an n-type heavily doped indium arsenide (InAs) are grown in this order on a Te-doped n-type gallium antimonide (GaSb) substrate 1. The GaSb substrate 1 in which Te is doped can be prepared by a lift-off method, a bridgman method, a vertical gradient solidification method, and a moving heater method.
In step S120, etching: the etched pattern is transferred to the sample containing the epitaxial layer by photolithography, exposure and development processes and then etched into the bottom contact layer 3.
In step S130, an ohmic contact electrode is prepared: the pattern of electrodes was transferred to the sample by photolithography, exposure and development processes. Evaporated electrode materials include, but are not limited to, titanium (Ti), platinum (Pt), gold (Au), copper (Cu), and nickel (Ni).
In step S140, passivation: the pattern of the passivation layer 9 is transferred to the sample by photolithography, exposure and development processes, and the passivation layer 9 material is grown on the mesa structure. The passivation layer 9 has a thickness of 200-500nm, and the passivation layer 9 material includes one of silicon dioxide (SiO 2) or silicon nitride (SiNx). The passivation layer 9 is used for protecting the side wall and preventing the surface of the device from oxidation, reducing the surface leakage current and improving the performance of the device.
Fig. 3 schematically shows a subband dispersion diagram of a bicolor infrared detector with an M-type superlattice as an absorption layer with different periodical layers at 0V bias according to an embodiment of the invention.
As shown in FIG. 3, the InAs/GaSb/AlSb/GaSb layer numbers shown in (a), (b), (c) and (d) in FIG. 3 have periods of 6/4/1/4MLs, 11/4/1/4MLs, 12/4/1/4MLs and 14/4/1/4MLs, respectively, and k is the wave number. The upper half of each graph is a conduction band, the lower half is a valence band, the band gap Eg is the distance from the bottom of the conduction band to the top of the valence band, the band gaps Eg of four different periodic layer structures are 240.0meV, 113.8meV, 99.2meV and 76.0meV in sequence, and the corresponding relation between the band gaps and the cut-off wavelength is that. It can be seen that different band gap Eg is generated by different thicknesses of the InAs layers in the InAs/GaSb/AlSb/GaSb periodic structure, and in practical application, the thicknesses of the InAs layers can be adjusted according to the target band gap value.
Fig. 4 schematically shows a sub-band dispersion diagram of a bicolor infrared detector with a 12/4/1/4MLs M-type superlattice as barrier layer 6 at a 0V bias in accordance with an embodiment of the invention.
As shown in fig. 4, the upper curve of fig. 4 is the conduction band, the lower curve is the valence band, the band gap Eg is the distance from the bottom of the conduction band to the top of the valence band, and k is the wavenumber. With the current structure, the bandgap Eg is 0.2851eV.
Fig. 5 schematically shows the absorption coefficient versus wavelength curve of a two-color infrared detector with an M-type superlattice of different InAs thicknesses as an absorption layer according to an embodiment of the invention.
As shown in FIG. 5, the InAs/GaSb/AlSb/GaSb layer periods shown in (a), (b), (c) and (d) in FIG. 5 are 6/4/1/4MLs, 11/4/1/4MLs, 12/4/1/4MLs and 14/4/1/4MLs, respectively, and it can be seen that the cut-off wavelengths of the four different periodic layer structures are 5 μm, 11 μm, 12 μm and 16 μm, respectively. The band gap Eg corresponds to the cutoff wavelength λ with eg=1.24/λ (eV), and the results of fig. 5 and 3 can correspond to each other.
Fig. 7 schematically illustrates energy band structure curves of a mid-long wave dual-color infrared detector under different bias voltages according to an embodiment of the present invention.
As shown in fig. 7, the abscissa indicates the positions corresponding to the different M-type superlattice layers, respectively, from low to high, the bottom contact layer3, the first absorption layer 4, the second absorption layer 5, the barrier layer 6, and the top contact layer 7; the ordinate is the energy values of the Conduction Band (CB), the Valence Band (VB), the electron fermi level (FC) and the hole fermi level (FV) curves. Fig. 7 (a) is an energy band structure curve of the mid-long wave bicolor infrared detector under a bias of 0V, and fig. 7 (b) is an energy band structure curve of the mid-long wave bicolor infrared detector under a bias of-0.2V.
Fig. 8 schematically illustrates energy band structure curves of a long-long wave bicolor infrared detector under different bias voltages according to an embodiment of the present invention.
As shown in fig. 8, the abscissa indicates the positions corresponding to the different M-type superlattice layers, respectively, from low to high, the bottom contact layer3, the first absorption layer 4, the second absorption layer 5, the barrier layer 6, and the top contact layer 7; the ordinate is the energy values of the Conduction Band (CB), the Valence Band (VB), the electron fermi level (FC) and the hole fermi level (FV) curves. Fig. 8 (a) is an energy band structure curve of the long-long wave bicolor infrared detector under a bias of 0V, and fig. 8 (b) is an energy band structure curve of the long-long wave bicolor infrared detector under a bias of-0.2V.
Fig. 9 schematically illustrates energy band structure curves of a long-very long wave bicolor infrared detector under different bias voltages according to an embodiment of the present invention.
As shown in fig. 9, the abscissa indicates the positions corresponding to the different M-type superlattice layers, respectively, from low to high, the bottom contact layer 3, the first absorption layer 4, the second absorption layer 5, the barrier layer 6, and the top contact layer 7; the ordinate is the energy values of the Conduction Band (CB), the Valence Band (VB), the electron fermi level (FC) and the hole fermi level (FV) curves. Fig. 9 (a) is an energy band structure curve of the long-very long wave bicolor infrared detector under a bias of 0V, and fig. 9 (b) is an energy band structure curve of the long-very long wave bicolor infrared detector under a bias of-0.2V.
Thus, embodiments of the present invention have been described in detail with reference to the accompanying drawings.
The foregoing embodiments have been provided for the purpose of illustrating the general principles of the present invention, and are more fully described herein with reference to the accompanying drawings, in which the principles of the present invention are shown and described, and in which the general principles of the invention are defined by the appended claims.
Claims (9)
1. A dual-color infrared detector, comprising:
a substrate, the material of the substrate comprising gallium antimonide material;
The buffer layer is positioned on the surface of the substrate;
a bottom contact layer located on a side of the buffer layer away from the substrate;
A first absorption layer positioned on one side of the bottom contact layer away from the substrate;
a second absorption layer positioned on one side of the first absorption layer away from the substrate;
A barrier layer located on a side of the second absorption layer away from the substrate;
A top contact layer located on a side of the barrier layer away from the substrate; and
A cap layer on a side of the top contact layer remote from the substrate,
The bottom contact layer, the first absorption layer, the second absorption layer, the barrier layer and the top contact layer are all M-shaped superlattice structures composed of indium arsenide, gallium antimonide, aluminum antimonide and gallium antimonide;
The buffer layer, the bottom contact layer, the first absorption layer, the second absorption layer, the barrier layer, the top contact layer and the cover layer are grown in a molecular beam epitaxy mode;
The periods of the M-type superlattice structures of the first absorption layer and the second absorption layer are different, so that the forbidden bandwidth of the first absorption layer is smaller than that of the second absorption layer, and the cut-off wavelength of the light detection of the first absorption layer is larger than that of the light detection of the second absorption layer;
The doping type of the first absorption layer is n-type doping, and the doping concentration is 5 multiplied by 10 15-5×1016cm-3;
The doping type of the second absorption layer is n-type or p-type doping, the doping type is determined by the detected wave band, and the doping concentration is 5 multiplied by 10 15-5×1016cm-3; and
The barrier layer is unintentionally doped, and is p-type doped with a concentration of 1×10 15-1×1016cm-3.
2. The dual-color infrared detector as set forth in claim 1, wherein,
The thickness ratio of each layer of indium arsenide, gallium antimonide, aluminum antimonide and gallium antimonide in the single period of the M-type superlattice structure of the bottom contact layer and the first absorption layer is the same; and/or the number of the groups of groups,
The thickness ratio of each layer of indium arsenide, gallium antimonide, aluminum antimonide and gallium antimonide in a single period of the M-type superlattice structure of the top contact layer and the second absorption layer is the same; and/or the number of the groups of groups,
The monolayer thickness of indium arsenide in the barrier layer material is less than the monolayer thickness of indium arsenide in the first absorber layer and the second absorber layer.
3. The dual-color infrared detector as claimed in claim 1 or 2, wherein,
The cutoff wavelength of the superlattice material of the barrier layer corresponds to a mid-wave infrared band; and/or the number of the groups of groups,
The conduction band vacuum energy level of the barrier layer is higher than that of the first absorption layer and the second absorption layer; and/or the number of the groups of groups,
The difference between the valence band vacuum energy level of the barrier layer and the valence band vacuum energy levels of the first absorption layer and the second absorption layer is less than 0.01eV; and/or the number of the groups of groups,
The band gap of the barrier layer is higher than that of the first absorption layer and the second absorption layer.
4. The dual-color infrared detector as claimed in claim 1 or 2, wherein,
The substrate material comprises tellurium-doped n-type gallium antimonide, and the tellurium doping concentration is 1 multiplied by 10 17-1×1018cm-3; and/or the number of the groups of groups,
The buffer layer material comprises tellurium-doped n-type gallium antimonide, and the tellurium doping concentration is 1 multiplied by 10 17-1×1018cm-3.
5. The dual-color infrared detector as claimed in claim 1 or 2, further comprising:
A first electrode located on one side of the bottom contact layer away from the substrate and on the outer side of the first absorption layer;
a second electrode located on a side of the cap layer away from the substrate; and
And the passivation layer is positioned on one side of the first absorption layer, the second absorption layer, the barrier layer, the outer surfaces of the top contact layer and the cover layer and one side of the bottom contact layer away from the substrate, and the passivation layer is disconnected at the first electrode and the second electrode.
6. The dual-color infrared detector as set forth in claim 5, wherein,
The doping type of the bottom contact layer is n-type doping, the doping concentration is1×10 17-1×1018cm-3, and the bottom contact layer and the first electrode form ohmic contact; and/or
The material of the cover layer comprises n-type doped indium arsenide with the doping concentration of 1 multiplied by 10 17-1×1018cm-3, and the cover layer forms ohmic contact with the second electrode.
7. A dual-color infrared detector as claimed in claim 1 or 2, comprising at least one of the following features:
The sum of the thicknesses of the first absorption layer and the second absorption layer is less than or equal to 4 mu m;
the thickness of the top contact layer is less than or equal to 1 mu m;
the thickness of the bottom contact layer is less than or equal to 1 mu m;
the thickness of the barrier layer is 1 μm or less.
8. The preparation method of the double-color infrared detector is characterized by comprising the following steps of:
And (3) epitaxial layer growth: sequentially epitaxially growing a buffer layer, a bottom contact layer, a first absorption layer, a second absorption layer, a barrier layer, a top contact layer and a cover layer on a substrate to obtain a sample containing an epitaxial layer;
Etching: transferring the etched pattern to a sample containing an epitaxial layer through photoetching, exposure and development processes, and then etching to the bottom contact layer;
preparing an ohmic contact electrode: transferring the pattern of the electrode to the sample by photolithography, exposure and development processes; and
Passivation: transferring the pattern of the passivation layer onto the sample by photolithography, exposure and development processes, growing a passivation layer material on the mesa structure,
Wherein the materials of the substrate and the buffer layer comprise gallium antimonide materials;
the bottom contact layer, the first absorption layer, the second absorption layer, the barrier layer and the top contact layer are all M-shaped superlattice structures composed of indium arsenide, gallium antimonide, aluminum antimonide and gallium antimonide;
The periods of the M-type superlattice structures of the first absorption layer and the second absorption layer are different, and the forbidden bandwidth of the first absorption layer is smaller than that of the second absorption layer, so that the cut-off wavelength of the light detection of the first absorption layer is larger than that of the light detection of the second absorption layer.
9. The method of claim 8, wherein the epitaxial layer growth is performed in a molecular beam epitaxy apparatus.
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