Superlattice infrared detector and preparation method thereof

Abstract

The invention relates to the technical field of semiconductor materials and devices, and provides a superlattice infrared detector which comprises a substrate and an epitaxial structure growing on the substrate. The epitaxial structure comprises a GaSb / Ga < 1-x > In < x > Sb superlattice buffer layer and an InAs / InAs < 1-y > Sby superlattice absorption layer, wherein the components of the GaSb / Ga < 1-x > In < x > Sb superlattice buffer layer are gradually changed, the InAs / InAs < 1-y > Sby superlattice absorption layer grows on the GaSb / Ga < 1-x > In < x > Sb superlattice buffer layer, and the InAs / InAs < 1-y > Sby superlattice absorption layer is matched with the lattice of the GaSb / Ga < 1-x > In < x > Sb superlattice buffer layer. The invention also provides a preparation method of the superlattice infrared detector. According to the invention, the GaSb / Ga1-xInxSb superlattice buffer layer with gradually changed components is introduced, the InAs / InAs1-ySby superlattice absorption layer grown on the buffer layer is improved, and the periodic thickness of the absorption layer is reduced, so that the absorption coefficient of the material of the absorption layer is improved, and the quantum efficiency of the device is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor materials and devices, and in particular to a superlattice infrared detector and a preparation method thereof. Background Art

[0002] Infrared detectors have important applications in military fields such as satellite reconnaissance, guidance, and night vision, as well as in civilian fields such as industrial detection, remote sensing, and medical detection. Although InAs / GaSb superlattice has been successfully applied to medium-wave, long-wave, and two-color infrared detection in recent years, it is limited by Ga-related defects, resulting in a short minority carrier lifetime and failure to achieve its theoretical performance.

[0003] The second type of InAs / InAsSb superlattice also has the characteristics of flexible band regulation, high uniformity, and low cost, and has achieved device cutoff wavelength coverage of 5μm to 13μm. Compared with the InAs / GaSb superlattice, the InAs / InAsSb heterojunction mainly contains two identical elements, In and As, and only Sb, which accounts for a small proportion, is a variable element. It has a simpler heterojunction interface structure and is easier to achieve high-quality crystal growth; and because it does not contain Ga atoms, it eliminates the defect states caused by Ga, making it have higher defect tolerance and longer minority carrier lifetime.

[0004] Compared with the InAs / GaSb type II superlattice, although InAs / InAsSb has a longer minority carrier lifetime, due to the difference in the hole quantum wells of the two, the valence band edge of GaSb is significantly higher than that of InAsSb, making the superlattice valence band edge higher and easier to achieve a small superlattice band gap. Therefore, the InAs / InAsSb superlattice infrared detector with GaSb as the buffer layer requires a longer period thickness of the InAs / InAsSb superlattice absorption layer to reach the long-wave or very long-wave band. The long period thickness InAs / InAsSb superlattice reduces the overlap of the electron-hole wave function, resulting in weaker oscillator strength and smaller absorption coefficient, which in turn affects the quantum efficiency of the device. Summary of the invention

[0005] The object of the present invention is to provide a superlattice infrared detector and a method for preparing the same, which can at least solve some of the defects in the prior art.

[0006] To achieve the above object, the embodiment of the present invention provides the following technical solution: a superlattice infrared detector, comprising a substrate and an epitaxial structure grown on the substrate, wherein the substrate is a GaSb substrate, and the epitaxial structure comprises a GaSb / Ga 1-x In x Sb superlattice buffer layer and a GaSb / Ga 1-x Inx InAs / InAs on Sb superlattice buffer layer 1-y Sb y Superlattice absorber layer, the InAs / InAs 1-y Sb y Superlattice absorber layer and the GaSb / Ga 1-x In x The lattice of the Sb superlattice buffer layer is matched.

[0007] Furthermore, the InAs / InAs 1-y Sb y The Sb composition in the superlattice absorption layer is greater than 10%.

[0008] Furthermore, the GaSb / Ga 1-x In x Sb superlattice buffer layer and the InAs / InAs 1-y Sb y In the superlattice absorption layer, the GaSb / Ga 1-x In x The number of atomic layers of GaSb in the Sb superlattice buffer layer is m, and Ga 1-x In x The number of atomic layers of Sb is n, and the InAs / InAs 1-y Sb y The number of InAs atoms in the superlattice absorption layer is M, and InAs 1-y Sb y The number of atomic layers is N, and the following relationship is satisfied between M, N, m, n, x and y:

[0009]

[0010] Among them, a GaSb 、a InSb 、a InAs are the lattice constants of GaSb, InSb, and InAs respectively.

[0011] Furthermore, the epitaxial structure further comprises a lower contact layer, a hole barrier layer, an electron barrier layer and an upper contact layer, and the GaSb / Ga 1-x In x Sb superlattice buffer layer, lower contact layer, hole barrier layer, InAs / InAs 1-y Sb y Superlattice absorption layer, electron barrier layer and upper contact layer.

[0012] Furthermore, the lower contact layer and the hole barrier layer both adopt an InAs / InAsSb superlattice structure, and the electron barrier layer adopts AlGaAsSb.

[0013] Furthermore, the InAs / InAs 1-y Sb y The lattice constant of the superlattice absorption layer is greater than the lattice constant of the GaSb substrate.

[0014] The embodiment of the present invention provides the following technical solution: a method for preparing a superlattice infrared detector, comprising the following steps:

[0015] Growth of composition-graded GaSb / Ga on GaSb substrate 1-x In x Sb superlattice buffer layer, followed by GaSb / Ga 1- x In x InAs / InAs grown on Sb superlattice buffer layer 1-y Sb y Superlattice absorber layer;

[0016] The InAs / InAs 1-y Sb y Superlattice absorber layer and the GaSb / Ga 1-x In x The lattice of the Sb superlattice buffer layer is matched.

[0017] Furthermore, the InAs / InAs 1-y Sb y The Sb composition in the superlattice absorption layer is greater than 10%.

[0018] Furthermore, the GaSb / Ga 1-x In x The Sb superlattice buffer layer is grown by digital alloying.

[0019] Further, in growing the GaSb / Ga 1-x In x When forming a Sb superlattice buffer layer, the temperature of the In source furnace is gradually increased so that the In beam current increases slowly and uniformly, forming a GaSb / GaSb / GaSb superlattice with a gradually increasing In content. 1-x In x Sb superlattice buffer layer.

[0020] Compared with the prior art, the invention has the following advantages: by introducing a GaSb / Ga 1- x In x Sb superlattice buffer layer, and the InAs / InAs grown on the buffer layer 1-y Sb yThe method of improving the superlattice absorption layer and reducing the periodic thickness of the absorption layer increases the absorption coefficient of the absorption layer material, thereby improving the quantum efficiency of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of a superlattice infrared detector provided by an embodiment of the present invention;

[0022] Figure 2 A 10GaSb / 5Ga superlattice infrared detector provided by an embodiment of the present invention 1-x In x Schematic diagram of the source furnace shutter switching sequence during the growth of the Sb superlattice buffer layer. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] See also Figure 1 The embodiment of the present invention provides a superlattice infrared detector, comprising a substrate and an epitaxial structure grown on the substrate, wherein the substrate is a GaSb substrate, and the epitaxial structure comprises a GaSb / Ga 1-x In x Sb superlattice buffer layer and a GaSb / Ga 1-x In x InAs / InAs on Sb superlattice buffer layer 1-y Sb y Superlattice absorber layer, the InAs / InAs 1-y Sb y Superlattice absorber layer and the GaSb / Ga 1-x In x In this embodiment, a composition-gradient GaSb / Ga 1-x In x Sb superlattice buffer layer, and the InAs / InAs grown on the buffer layer 1-y Sb y The method of improving the superlattice absorption layer and reducing the periodic thickness of the absorption layer increases the absorption coefficient of the absorption layer material, thereby improving the quantum efficiency of the device. 1-y Sb ySuperlattice, higher Sb content can achieve longer cut-off wavelength, while reducing the thickness of InAs, can make the single period thickness of the absorption region superlattice thinner, thereby increasing the alternation of electron-hole wave function and obtaining a larger absorption coefficient. However, with the increase of Sb content, InAs / InAs 1-y Sb y The larger the average lattice constant of the superlattice, the greater the mismatch with the GaSb substrate. This embodiment cleverly introduces a composition gradient GaSb / Ga 1-x In x The Sb superlattice buffer layer can effectively relieve the strain between the InAs / InAsSb superlattice epitaxial layer and the buffer layer. At the same time, the Sb component in the absorption region superlattice can be increased, and the corresponding cutoff wavelength can be achieved at a thinner period thickness. The superlattice epitaxial layer can include InAs / InAs 1-y Sb y The superlattice absorption layer, superlattice hole barrier layer, and superlattice lower contact layer all adopt InAs / InAsSb superlattice structure. Therefore, the lower contact layer can be regarded as the lower layer of the absorption layer. Since the substrate composition is fixed, when the absorption layer wants to increase the Sb component, it will cause the lower contact layer under the absorption layer to mismatch with the buffer layer. In order to maintain the lattice matching with the buffer layer, it is necessary to increase the periodic thickness of the absorption layer, and the light absorption and light response will decrease, affecting the quantum efficiency of the device. This embodiment cleverly introduces the composition gradient GaSb / Ga 1-x In x Sb superlattice buffer layer, which can be adjusted according to the Sb composition change of the absorption layer GaSb / Ga 1-x In x The In component of the Sb superlattice buffer layer maintains lattice matching between the absorption layer and the buffer layer and maintains strain balance.

[0025] In the prior art, InAs / InAsSb superlattice infrared detectors use GaSb as a buffer layer. In order to maintain the strain balance between the absorption layer and the buffer layer, the Sb component in the InAs / InAsSb superlattice absorption layer is generally 10%. Under this Sb component, a longer period thickness of the InAs / InAsSb superlattice absorption layer is required to reach the long-wave or very long-wave band. The long period thickness InAs / InAsSb superlattice reduces the overlap of the electron-hole wave function, resulting in weaker oscillator strength and smaller absorption coefficient, which in turn affects the quantum efficiency of the device. Please refer to Figure 1 In the present invention, the InAs / InAs 1-y Sb y The Sb component in the superlattice absorption layer increases, and the InAs / InAs 1-y Sb yThe Sb content in the superlattice absorption layer is greater than 10%. 1-x In x The In component in the Sb superlattice buffer layer is such that the InAs / InAs 1- y Sb y Superlattice absorber layer and the GaSb / Ga 1-x In x The lattice matching of the Sb superlattice buffer layer can achieve the corresponding cutoff wavelength at a thinner absorption layer period thickness. 1-y Sb y There are two ways to keep the Sb component in the superlattice absorption layer. One is to keep the InAs 1-y Sb y The Sb content in the medium remains unchanged (i.e., y remains unchanged), reducing the single-period InAs and InAs 1-y Sb y The atomic layer ratio is to maintain the single period InAs and InAs 1-y Sb y The atomic layer ratio remains unchanged, and InAs is added 1-y Sb y In addition, it should be noted that for MInAs / NInAs 1-y Sb y In the superlattice absorption layer, when the M / N ratio and the y value are fixed, the wavelength increases nonlinearly with the increase of the period thickness (i.e., M+N). 1-y Sb y The lattice constant of the superlattice absorption layer is greater than the lattice constant of the GaSb substrate.

[0026] See also Figure 1 , for mGaSb / nGa 1-x In x Sb superlattice buffer layer and MInAs / NInAs 1-y Sb y In the superlattice absorption layer, when the lattice constants a of the two are equal, the following relationship is satisfied between M, N, m, n, x and y:

[0027]

[0028] Among them, a GaSb 、a InSb 、a InAs are the lattice constants of GaSb, InSb, and InAs, respectively; m and n are mGaSb / nGa 1- x In xGaSb and Ga in a single period of Sb superlattice 1-x In x The number of atomic layers of Sb; M and N are MInAs / NInAs respectively 1-y Sb y InAs and InAs in a single period of superlattice 1-y Sb y The number of atomic layers; x and y are the superlattice single layer Ga 1-x In x Sb、InAs 1-y Sb y The lattice constant a is the lattice constant of a binary compound, which is generally a constant and changes only slightly with temperature. The superlattice of this embodiment is composed of two compounds, and M, N, m, and n represent the number of layers of each component compound in a single period superlattice. For example, the GaSb / GaInSb superlattice is composed of two compounds, GaSb and GaInSb, to form a period.

[0029] According to this relationship, GaSb / Ga 1-x In x The Sb superlattice buffer layer can be based on the InAs / InAs 1-y Sb y The composition of Sb in the superlattice absorption layer is matched and regulated to reduce the periodic thickness of the absorption layer, thereby increasing the absorption coefficient of the absorption layer and thus improving the quantum efficiency of the device. 1-x In x The Sb superlattice buffer layer only introduces a small amount of In, and the content is low. The growth adhesion coefficient of the group III elements Ga and In can be effectively controlled to 1. There is no competition, and the growth is easy to control, which has good application prospects.

[0030] See also Figure 1 The epitaxial structure further includes a lower contact layer, a hole barrier layer and an electron barrier layer, and the GaSb / Ga 1-x In x Sb superlattice buffer layer, lower contact layer, hole barrier layer, InAs / InAs 1-y Sb y Preferably, the lower contact layer and the hole barrier layer both adopt an InAs / InAsSb superlattice structure, and the electron barrier layer adopts an InAsSb structure. The epitaxial structure also includes an upper contact layer and a cap layer sequentially grown on the electron barrier layer. In this embodiment, the superlattice infrared detector specifically includes GaSb / GaSb grown sequentially on a GaSb substrate. 1-x In xSb superlattice buffer layer, InAs / InAsSb superlattice lower contact layer, InAs / InAsSb superlattice hole barrier layer, InAs / InAs 1-y Sb y Superlattice absorption layer, AlGaAsSb electron barrier layer, upper contact layer and cap layer.

[0031] See also Figure 1 The present invention also provides a method for preparing a superlattice infrared detector, which is used to prepare the above-mentioned superlattice infrared detector, wherein the superlattice infrared detector is a long-wave superlattice infrared detector. Specifically, the method comprises the following steps: growing a GaSb / GaSb substrate with a gradient composition; 1-x In x Sb superlattice buffer layer, followed by GaSb / Ga 1-x In x InAs / InAs grown on Sb superlattice buffer layer 1-y Sb y Superlattice absorption layer; the InAs / InAs 1-y Sb y Superlattice absorber layer and the GaSb / Ga 1-x In x The lattice of the Sb superlattice buffer layer matches. In this embodiment,

[0032] See also Figure 1 , the GaSb / Ga 1-x In x The Sb superlattice buffer layer is grown by digital alloying. 1-x In x The Sb superlattice buffer layer is epitaxially grown using a digital alloy method, which can effectively release stress, isolate threading dislocations, and improve the crystal quality and device performance of the epitaxial material above the buffer layer.

[0033] See also Figure 1 , in the growth of the GaSb / Ga 1-x In x When forming a Sb superlattice buffer layer, the temperature of the In source furnace is gradually increased so that the In beam current increases slowly and uniformly, forming a GaSb / GaSb / GaSb superlattice with a gradually increasing In content. 1-x In x Sb superlattice buffer layer.

[0034] The following is a specific implementation method:

[0035] Two rounds of InAs / InAs growth were performed under the same growth conditions. 0.5 Sb 0.5 Superlattice long-wave materials.

[0036] The buffer layer of sample A is GaSb material with a lattice constant of 0.6096nm. In order to maintain lattice matching with the buffer layer, the single-period structure of the absorption region is designed to be 25.6InAs / 6.4InAs 0.5 Sb 0.5 , the Sb component in the absorption region is 0.1, i.e. 10%, of which InAs and InAs 0.5 Sb 0.5 The atomic layer ratio is 4:1, and the total number of atomic layers in a single period is 32ML, at this time 25.6InAs / 6.4InAs 0.5 Sb 0.5 The lattice constant of the superlattice is 0.6100nm, which basically matches the GaSb buffer layer lattice.

[0037] The buffer layer of sample B is epitaxially grown on a GaSb substrate using a digital alloy method to form a gradient 10GaSb / 5Ga layer with a thickness of about 1.5 μm. 1-x In x Sb superlattice, the source furnace shutter switch during the growth process is as follows Figure 2 As shown in the figure, as the In source furnace gradually heats up, the In beam current increases slowly and uniformly, and the Ga / In beam current ratio increases from nearly 100 / 1 in the first cycle to 3 / 1 in the last cycle, that is, the x value gradually increases from 0 to 0.25, and the In component in the buffer layer gradually increases from 0 to 0.083, and the 10GaSb / 5Ga in the top layer 0.75 In 0.25 The lattice constant of the Sb superlattice is 0.6128nm, and the single-period structure of the absorption region is designed to be 16InAs / 8InAs 0.5 Sb 0.5 The Sb component in the absorption region is 0.167, which is greater than 10%, and the lattice constant is also 0.6128nm, which can match the buffer layer lattice. This structure can make InAs and InAs 0.5 Sb 0.5 The atomic layer ratio is 2:1, and the total number of atomic layers in a single period is 24ML.

[0038] The same preparation process was used to prepare the unit device of sample A and sample B, and the spectrum and photoresponse were tested under the same conditions. The results show that the 50% cut-off wavelength of both is about 9.5μm, and the photoresponse of sample B is 20% larger than that of sample A. This shows that sample B has increased light absorption and thus improved photoresponse due to the reduction of the single-period thickness of the superlattice absorption layer.

[0039] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A superlattice infrared detector, comprising a substrate and an epitaxial structure grown on the substrate, characterized in that: The substrate is a GaSb substrate, and the epitaxial structure includes a GaSb / Ga 1-x In x Sb superlattice buffer layer and a GaSb / Ga 1-x In x InAs / InAs on Sb superlattice buffer layer 1-y Sb y Superlattice absorber layer, the InAs / InAs 1-y Sb y Superlattice absorber layer and the GaSb / Ga 1-x In x The lattice of the Sb superlattice buffer layer is matched.

2. A superlattice infrared detector according to claim 1, characterized in that: The InAs / InAs 1-y Sb y The Sb composition in the superlattice absorption layer is greater than 10%.

3. A superlattice infrared detector according to claim 1, characterized in that: The GaSb / Ga 1-x In x Sb superlattice buffer layer and the InAs / InAs 1-y Sb y In the superlattice absorption layer, the GaSb / Ga 1-x In x The number of atomic layers of GaSb in the Sb superlattice buffer layer is m, and Ga 1-x In x The number of atomic layers of Sb is n, and the InAs / InAs 1-y Sb y The number of InAs atoms in the superlattice absorption layer is M, and InAs 1-y Sb y The number of atomic layers is N, and the following relationship is satisfied between M, N, m, n, x and y: Among them, a GaSb 、a InSb 、a InAs are the lattice constants of GaSb, InSb, and InAs respectively.

4. The superlattice infrared detector according to claim 1, characterized in that: The epitaxial structure also includes a lower contact layer, a hole barrier layer, an electron barrier layer and an upper contact layer. The GaSb / Ga 1-x In x Sb superlattice buffer layer, lower contact layer, hole barrier layer, InAs / InAs 1-y Sb y Superlattice absorption layer, electron barrier layer and upper contact layer.

5. A superlattice infrared detector as claimed in claim 4, characterized in that: The lower contact layer and the hole barrier layer both adopt an InAs / InAsSb superlattice structure, and the electron barrier layer adopts AlGaAsSb.

6. The superlattice infrared detector according to claim 1, characterized in that: The InAs / InAs 1-y Sb y The lattice constant of the superlattice absorption layer is greater than the lattice constant of the GaSb substrate.

7. A method for preparing a superlattice infrared detector, characterized in that: The following steps are involved: Growth of composition-graded GaSb / Ga on GaSb substrate 1-x In x Sb superlattice buffer layer, followed by GaSb / Ga 1-x In x InAs / InAs grown on Sb superlattice buffer layer 1-y Sb y Superlattice absorber layer; The InAs / InAs 1-y Sb y Superlattice absorber layer and the GaSb / Ga 1-x In x The lattice of the Sb superlattice buffer layer is matched.

8. The method for preparing a superlattice infrared detector according to claim 7, characterized in that: The InAs / InAs 1-y Sb y The Sb composition in the superlattice absorption layer is greater than 10%.

9. The method for preparing a superlattice infrared detector according to claim 7, characterized in that: The GaSb / Ga 1-x In x The Sb superlattice buffer layer is grown by digital alloying.

10. The method for preparing a superlattice infrared detector according to claim 7, characterized in that: In growing the GaSb / Ga 1-x In x When forming a Sb superlattice buffer layer, the temperature of the In source furnace is gradually increased so that the In beam current increases slowly and uniformly, forming a GaSb / GaSb / GaSb superlattice with a gradually increasing In content. 1-x In x Sb superlattice buffer layer.

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