A method for growing a type ii superlattice infrared detector based on MBE

Abstract

The application relates to the field of semiconductor device design and manufacturing, and discloses a method for growing a second-type superlattice infrared detector based on MBE, which comprises the following steps: a semiconductor substrate; a buffer layer arranged above the semiconductor substrate; an N-type lower electrode contact layer located above the buffer layer; a medium-wave infrared absorption layer located above the N-type lower electrode contact layer; an electron barrier layer located above the medium-wave infrared absorption layer; a short-wave infrared absorption layer located above the electron barrier layer; an N-type upper electrode contact layer located above the short-wave infrared absorption layer; a Cap layer located above the N-type upper electrode contact layer; an electrode layer, wherein an upper electrode is located above the Cap layer; a lower electrode is in contact with the N-type lower electrode contact layer; and a passivation layer covers the sidewall of the detector. The different absorption layers are separated by the electron barrier layer, the cross-talk effect between different wave bands is reduced, the false alarm rate of the detector in a complex environment is reduced, and the detector can still maintain high precision in a high-interference environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor device design and manufacturing, in particular to a method for growing a type-II superlattice infrared detector based on MBE. BACKGROUND

[0002] InAs / GaSb type-II superlattice is considered as the first choice of the third generation infrared focal plane detector. In recent years, the United States, Germany, Japan and other countries have been actively promoting infrared detection technology based on the type-II superlattice. InAs / GaSb hetero material system has a unique energy band structure. The band gap of InAs is smaller than the valence band offset of InAs / GaSb, so the conduction band bottom of InAs is below the valence band top of GaSb, forming a type-II superlattice structure. This causes the spatial separation of electrons and holes, with electrons confined in InAs layers and holes confined in GaSb layers, and the effective band gap is the energy difference between the electron miniband and the heavy hole miniband. Mature III-V compound molecular beam epitaxy growth technology provides technical support for the preparation of high-performance type-II superlattice. More importantly, the type-II superlattice material system provides more design possibilities for detector structures, with a band gap of 2-30 μm, which can be used to prepare short-wave, medium-wave, long-wave, very long-wave, dual-color segment and multi-band devices.

[0003] However, the current InAs / GaSb type-II superlattice detector has insufficient detection capability in complex environments, resulting in a high false alarm rate. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a method for growing a type-II superlattice infrared detector based on MBE, which solves the problem of high false alarm rate caused by the current InAs / GaSb type-II superlattice detector.

[0005] To achieve the above purpose, the present application realizes the following technical scheme: a type-II superlattice infrared detector based on MBE growth, comprising:

[0006] Semiconductor substrate: the semiconductor substrate is made of GaSb material;

[0007] Buffer layer: disposed above the semiconductor substrate, made of GaSb material;

[0008] N-type lower electrode contact layer: located above the buffer layer, the N-type lower electrode contact layer is an InAs / GaSb superlattice structure, which is doped to form an N-type conductive layer;

[0009] Mid-wave infrared absorption layer: located above the N-type lower electrode contact layer, the mid-wave infrared absorption layer is an InAs / GaSb superlattice structure;

[0010] Electron barrier layer: located above the middle wave infrared absorption layer, the electron barrier layer is AlGaAs material;

[0011] Short wave infrared absorption layer: located above the electron barrier layer, the short wave infrared absorption layer is InAs / GaSb superlattice structure, and is not doped;

[0012] N-type upper electrode contact layer: located above the short wave infrared absorption layer, the N-type upper electrode contact layer is InAs / GaSb superlattice structure, and is doped to form an N-type conductive layer;

[0013] Cap layer: located above the N-type upper electrode contact layer, the Cap layer is InAs material, and is doped to form an ohmic contact layer of the upper electrode;

[0014] Electrode layer: upper electrode: located above the Cap layer, made of Ti / Au alloy; lower electrode: connected with the N-type lower electrode contact layer, made of Ti / Au alloy;

[0015] Passivation layer: covering the sidewall of the detector, the passivation material is silicon dioxide and aluminum oxide.

[0016] Preferably, a preparation method of a two-type superlattice infrared detector based on MBE growth includes the following steps:

[0017] S1: pretreatment of GaSb substrate

[0018] The GaSb substrate is placed in the MBE growth system, and first high-temperature oxygen removal treatment is performed;

[0019] S2: growth of GaSb buffer layer

[0020] A GaSb buffer layer is epitaxially grown on the pretreated GaSb substrate;

[0021] S3: growth of N-type lower electrode contact layer

[0022] An InAs / GaSb superlattice structure is grown on the GaSb buffer layer, the InAs / GaSb superlattice structure is composed of 10 layers of InAs and 10 layers of GaSb stacked alternately;

[0023] S4: growth of middle wave infrared absorption layer

[0024] A middle wave infrared absorption layer is grown on the N-type lower electrode contact layer, the middle wave infrared absorption layer also adopts InAs / GaSb superlattice structure;

[0025] S5: growth of electron barrier layer

[0026] In order to separate the detection areas of different wavebands, an Al 0.2 Ga0.8 As an electron barrier layer;

[0027] S6: Growth of a short-wave infrared absorption layer

[0028] A short-wave infrared absorption layer is grown on top of the electron barrier layer, which is an InAs / GaSb superlattice structure with 7 layers of InAs and 7 layers of GaSb stacked alternately, without being doped;

[0029] S7: Growth of an N-type upper electrode contact layer

[0030] An InAs / GaSb superlattice structure is grown on top of the short-wave infrared absorption layer, which is composed of 7 layers of InAs and 6 layers of GaSb stacked alternately;

[0031] S8: Growth of a Cap layer

[0032] An InAs Cap layer is grown on top of the N-type upper electrode contact layer;

[0033] S9: Passivation treatment

[0034] After the device is grown, a multi-step passivation process is used to treat the sidewalls of the device;

[0035] S10: Electrode fabrication

[0036] The electrode material is selected to be Ti / Au alloy. First, a Ti layer is deposited on the surface of the device using electron beam evaporation technology, and then an Au layer is deposited to form an electrode structure.

[0037] Preferably, in the S1 step, the substrate is heated to 520-550°C, and the temperature is maintained to remove the oxide layer on the surface of the substrate.

[0038] Preferably, in the S2 step, the thickness of the GaSb buffer layer grown by epitaxy is 300-600 nm, and this process is performed using molecular beam epitaxy technology. The doping source of the buffer layer is selected to be Te, and the doping concentration is controlled to be 2×10 18 cm -3 .

[0039] Preferably, in the S3 step, the thickness of the InAs / GaSb superlattice structure grown is 0.3-0.5 μm, and both the InAs and GaSb layers are doped with Si, with a doping concentration of 2×10 18 cm -3 , and in the S4 step, the thickness of the mid-wave infrared absorption layer is 2-4 μm.

[0040] Preferably, in the S4 step, the thickness of the mid-wave infrared absorption layer grown on the N-type lower electrode contact layer is 2-4 μm; and in the S5 step, the thickness of the Al 0.2Ga 0.8 The thickness of the As electronic barrier layer is 0.3-0.5 μm.

[0041] Preferably, in step S6, the thickness of the short-wave infrared absorption layer is 2.5-5 μm.

[0042] Preferably, in step S7, the thickness of the InAs / GaSb superlattice structure is 0.3-0.5 μm, and this region is also doped with Si, with the doping concentration controlled at 2 × 10⁻⁶. 18 cm -3 In step S8, the InAs Cap layer has a thickness of 30 nm and a doping concentration of 2 × 10⁻⁶. 18 cm -3 .

[0043] Preferably, in step S9, firstly, the device sidewall is subjected to dangling bond saturation treatment by anodic sulfidation, then a 0.2 μm thick silicon dioxide layer is deposited for passivation protection, and finally a 0.03 μm thick Al2O3 layer is deposited.

[0044] Preferably, in step S10, the Ti layer is 200 nm thick and the Au layer is 1200 nm thick.

[0045] This invention provides a method for growing a type-II superlattice infrared detector based on MBE. It has the following beneficial effects:

[0046] 1. This invention uses an electronic barrier layer to separate different absorption layers, which reduces crosstalk effects between different bands and thus lowers the false alarm rate of the detector in complex environments. This feature enables the detector to maintain high accuracy even in high interference environments.

[0047] 2. This invention utilizes a type-II superlattice structure of InAs / GaSb, which enables efficient infrared detection. The special band structure of the type-II superlattice separates electrons and holes, reducing non-radiative recombination and thus improving the detector's responsivity and sensitivity.

[0048] 3. This invention achieves dual-color or multi-band infrared detection by integrating absorption layers of different bands (such as mid-wave and short-wave absorption layers). The absorption layers of different bands can detect information from multiple infrared bands simultaneously, thereby improving the application range and flexibility of the detector. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the device structure of a type II superlattice infrared detector based on MBE growth according to the present invention;

[0050] Figure 2 This is a schematic diagram of the AFM of the present invention;

[0051] Figure 3 This is a schematic diagram of the IV curve of the present invention;

[0052] Figure 4 This is a schematic diagram of the band structure of the present invention.

[0053] The components are: 1. Semiconductor substrate; 2. Buffer layer; 3. N-type lower electrode contact layer; 4. Mid-wave infrared absorption layer; 5. Electron barrier layer; 6. Short-wave infrared absorption layer; 7. N-type upper electrode contact layer; 8. Cap layer; 9. Electrode layer; 10. Passivation layer. Detailed Implementation

[0054] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] Please see the appendix Figure 1 This invention provides a type II superlattice infrared detector based on MBE growth, comprising:

[0056] Semiconductor substrate 1: The semiconductor substrate is made of GaSb material and is used to support and provide a substrate for epitaxial growth;

[0057] Buffer layer 2: disposed above semiconductor substrate 1, the buffer layer is made of GaSb material, used to improve the interface quality between the substrate and the upper structure;

[0058] N-type lower electrode contact layer 3: Located above buffer layer 2, N-type lower electrode contact layer 3 is an InAs / GaSb superlattice structure, which is doped to form an N-type conductive layer;

[0059] Mid-wave infrared absorption layer 4: Located above the N-type lower electrode contact layer 3, the mid-wave infrared absorption layer 4 is an InAs / GaSb superlattice structure used to absorb mid-wave infrared light;

[0060] Electron barrier layer 5: Located above the mid-wave infrared absorption layer 4, the electron barrier layer 5 is made of AlGaAs material and is used to separate the mid-wave infrared absorption layer from the short-wave infrared absorption layer to reduce crosstalk between different bands.

[0061] Short-wave infrared absorption layer 6: Located above the electronic barrier layer 5, the short-wave infrared absorption layer 6 is an InAs / GaSb superlattice structure, undoped, and used to absorb short-wave infrared light;

[0062] N-type upper electrode contact layer 7: Located above the short-wave infrared absorption layer 6, the N-type upper electrode contact layer 7 is an InAs / GaSb superlattice structure, which is formed by doping to form an N-type conductive layer.

[0063] Cap layer 8: Located above the N-type upper electrode contact layer 7, Cap layer 8 is made of InAs material and is doped to form the ohmic contact layer of the upper electrode.

[0064] Electrode layer 9: Upper electrode, located above Cap layer 8, made of Ti / Au alloy, used to provide external electrical connection;

[0065] The lower electrode, which is in contact with the N-type lower electrode contact layer 7, is made of Ti / Au alloy and is used to form circuit connections;

[0066] Passivation layer 10: Covers the sidewall of the detector. The passivation materials are silicon dioxide and aluminum oxide. It is used to protect the sidewall of the device and reduce the impact of surface states on the device performance.

[0067] A method for fabricating a type-II superlattice infrared detector based on MBE growth includes the following steps:

[0068] S1: Pretreatment of GaSb substrate:

[0069] The GaSb substrate is placed in the MBE growth system and first undergoes a high-temperature deoxidation process. Specifically, the substrate is heated to 520-550°C and continuously processed at this temperature to remove the oxide layer on the substrate surface, ensuring interface quality during subsequent growth processes.

[0070] S2: Growth of the GaSb buffer layer:

[0071] A 300-600 nm thick GaSb buffer layer was epitaxially grown on the pretreated GaSb substrate. This process was performed using molecular beam epitaxy, with Te selected as the dopant source and the doping concentration controlled at 2 × 10⁻⁶ nm. 18 cm -3 To optimize the conductivity and crystal quality of the buffer layer.

[0072] S3: Growth of N-type lower electrode contact layer:

[0073] A 0.3-0.5 μm thick InAs / GaSb superlattice structure is grown on the GaSb buffer layer. This structure consists of 10 alternating layers of InAs and 10 alternating layers of GaSb. Both the InAs and GaSb layers are doped with Si at a concentration of 2 × 10⁻⁶. 18 cm -3 This superlattice structure, serving as the N-type lower electrode contact layer, provides a good conductive path for subsequent electron transport.

[0074] S4: Growth of the mid-infrared absorption layer:

[0075] A mid-wave infrared absorption layer with a thickness of 2-4 μm is grown on the N-type lower electrode contact layer. This absorption layer also adopts an InAs / GaSb superlattice structure, and the thickness of each InAs and GaSb layer is precisely controlled to ensure effective absorption of mid-wave infrared light.

[0076] S5: Growth of the electron barrier layer:

[0077] To separate the detection regions for different wavelength bands, an Al layer with a thickness of 0.3-0.5 μm was grown on the mid-wave absorption layer. 0.2 Ga 0.8 As an electronic barrier layer. This barrier layer, by adjusting the ratio of Al and Ga, forms an effective barrier, reducing crosstalk between different bands and improving the selectivity of the detector.

[0078] S6: Growth of the short-wave infrared absorption layer:

[0079] A short-wave infrared absorption layer with a thickness of 2.5-5 μm is grown on top of an electronic barrier layer. This absorption layer adopts a superlattice structure of 7 layers of InAs and 7 layers of GaSb stacked alternately, without doping, in order to maintain the intrinsic properties of the material and ensure efficient absorption of short-wave infrared light.

[0080] S7: Growth of the N-type upper electrode contact layer:

[0081] A 0.3-0.5 μm thick InAs / GaSb superlattice structure was grown on top of the short-wave infrared absorption layer. The structure consisted of 7 alternating InAs layers and 6 GaSb layers. This region was also doped with Si, with the doping concentration controlled at 2 × 10⁻⁶. 18 cm -3 It is used to form the N-type upper electrode contact layer.

[0082] S8: Growth of the Cap layer:

[0083] A 30 nm thick InAs Cap layer with a doping concentration of 2 × 10⁻⁶ was grown on top of the N-type upper electrode contact layer. 18 cm -3 The Cap layer is used to enhance ohmic contacts, ensuring good contact performance between the electrode and the semiconductor material.

[0084] S9: Passivation treatment:

[0085] After the device is grown, a multi-step passivation process is used to treat the sidewalls of the device. First, the sidewalls of the device are saturated with dangling bonds by anodic sulfidation. Then, a 0.2 μm thick silicon dioxide layer is deposited for passivation protection. Finally, a 0.03 μm thick Al2O3 layer is deposited to further improve the durability and stability of the device.

[0086] S10: Electrode fabrication:

[0087] Ti / Au alloy was chosen as the electrode material. First, a 200 nm thick Ti layer was deposited on the device surface using electron beam evaporation, followed by a 1200 nm thick Au layer to form the electrode structure. This process ensures good contact and conductivity between the electrode and the semiconductor material.

[0088] Experimental results

[0089] Epitaxially grown epitaxial wafers at 10 × 10 μm 2 Within the specified range, the surface roughness RMS is 0.19 nm, and the surface exhibits obvious step flow, indicating good epitaxial wafer growth. (Reference) Figure 2 .

[0090] Dark current refers to the current that exists within electronic devices and persists even without external light. This current is primarily caused by impurities, defects, or thermally excited charge carriers, rather than being affected by external light. Figure 3 The results show the device current response under both illumination and no illumination, clearly demonstrating light response under both forward and reverse bias.

[0091] pass Figure 4 We can see that the potential barrier separates the two different detection channels, greatly reducing crosstalk between different bands.

[0092] Summary of conclusions

[0093] By superimposing two different mid-wave infrared detectors, it is possible to detect two different infrared bands, which provides a guiding idea for achieving detection in more bands.

[0094] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A type II superlattice infrared detector based on MBE growth, characterized in that, include: Semiconductor substrate (1): Semiconductor substrate (1) is made of GaSb material; Buffer layer (2): disposed above semiconductor substrate (1), and is made of GaSb material; N-type lower electrode contact layer (3): Located above the buffer layer (2), the N-type lower electrode contact layer (3) is an InAs / GaSb superlattice structure, which is formed by doping to form an N-type conductive layer; Mid-wave infrared absorption layer (4): Located above the N-type lower electrode contact layer (3), the mid-wave infrared absorption layer (4) is an InAs / GaSb superlattice structure; Electron barrier layer (5): Located above the mid-wave infrared absorption layer (4), the electron barrier layer (5) is made of AlGaAs material; Short-wave infrared absorption layer (6): Located above the electronic barrier layer (5), the short-wave infrared absorption layer (6) is an InAs / GaSb superlattice structure and is undoped; N-type upper electrode contact layer (7): Located above the short-wave infrared absorption layer (6), the N-type upper electrode contact layer (7) is an InAs / GaSb superlattice structure, which is formed by doping to form an N-type conductive layer; Cap layer (8): Located above the N-type upper electrode contact layer (7), the Cap layer (8) is made of InAs material and is formed by doping to form the ohmic contact layer of the upper electrode. Electrode layer (9): Upper electrode: Located above the Cap layer (8), made of Ti / Au alloy; Lower electrode: It is in contact with the N-type lower electrode contact layer (3) and is made of Ti / Au alloy; Passivation layer (10): Covers the sidewall of the detector, and the passivation material is silicon dioxide and aluminum oxide.

2. A method for fabricating a type-II superlattice infrared detector based on MBE growth, as described in claim 1, characterized in that, Includes the following steps: S1: Pretreatment of GaSb substrate The GaSb substrate was placed in the MBE growth system and first underwent high-temperature deoxygenation treatment. S2: Growth of GaSb buffer layer (2) A GaSb buffer layer is epitaxially grown on the pretreated GaSb substrate (2). S3: Growth of N-type lower electrode contact layer (3) On the GaSb buffer layer (2), an InAs / GaSb superlattice structure is grown, which is composed of 10 layers of InAs and 10 layers of GaSb stacked alternately. S4: Growth of the mid-wave infrared absorption layer (4) A mid-wave infrared absorption layer (4) is grown on the N-type lower electrode contact layer (3), and the mid-wave infrared absorption layer (4) also adopts the InAs / GaSb superlattice structure. S5: Growth of the electron barrier layer (5) To separate the detection areas of different wavelengths, an Al layer is grown on the mid-wave infrared absorption layer (4). 0.2 Ga 0.8 As electron barrier layer (5); S6: Growth of the short-wave infrared absorption layer (6) A short-wave infrared absorption layer (6) is grown on top of the electronic barrier layer (5). The short-wave infrared absorption layer (6) adopts a superlattice structure of 7 layers of InAs and 7 layers of GaSb stacked alternately, without doping. S7: Growth of the N-type upper electrode contact layer (7) An InAs / GaSb superlattice structure is grown on the short-wave infrared absorption layer (6), which is composed of 7 layers of InAs and 6 layers of GaSb stacked alternately. S8: Growth of Cap layer (8) An InAs Cap layer (8) is grown on top of the N-type upper electrode contact layer (7); S9: Passivation treatment After the device is grown, a multi-step passivation process is used to treat the sidewalls of the device; S10: Electrode fabrication The electrode material is a Ti / Au alloy. First, a Ti layer is deposited on the device surface using electron beam evaporation technology, followed by the deposition of an Au layer to form the electrode structure.

3. The method for fabricating a type-II superlattice infrared detector based on MBE growth according to claim 2, characterized in that, In step S1, the specific operation is to heat the substrate to 520-550°C and continuously process it at this temperature to remove the oxide layer on the substrate surface.

4. The method for fabricating a type-II superlattice infrared detector based on MBE growth according to claim 2, characterized in that, In step S2, the thickness of the epitaxially grown GaSb buffer layer (2) is 300-600 nm. This process is carried out using molecular beam epitaxy. The doping source for the buffer layer (2) is Te, and the doping concentration is controlled at 2×10⁻⁶. 18 cm -3 .

5. The method for fabricating a type-II superlattice infrared detector based on MBE growth according to claim 2, characterized in that, In step S3, the thickness of the grown InAs / GaSb superlattice structure is 0.3-0.5 μm, and both the InAs and GaSb layers are doped with Si at a concentration of 2 × 10⁻⁶. 18 cm -3 In step S4, the thickness of the mid-wave infrared absorption layer (4) is 2-4 μm.

6. The method for fabricating a type-II superlattice infrared detector based on MBE growth according to claim 2, characterized in that, In step S4, the thickness of the mid-wave infrared absorption layer (4) grown on the N-type lower electrode contact layer (3) is 2-4 μm; in step S5, Al 0.2 Ga 0.8 The thickness of the As electronic barrier layer (5) is 0.3-0.5 μm.

7. The method for fabricating a type-II superlattice infrared detector based on MBE growth according to claim 2, characterized in that, In step S6, the thickness of the short-wave infrared absorption layer (6) is 2.5-5 μm.

8. The method for fabricating a type-II superlattice infrared detector based on MBE growth according to claim 2, characterized in that, In step S7, the thickness of the InAs / GaSb superlattice structure is 0.3-0.5 μm, and this region is also doped with Si, with the doping concentration controlled at 2 × 10⁻⁶. 18 cm -3 In step S8, the InAs Cap layer (8) has a thickness of 30 nm and a doping concentration of 2 × 10⁻⁶. 18 cm -3 .

9. The method for fabricating a type-II superlattice infrared detector based on MBE growth according to claim 2, characterized in that, In step S9, firstly, the sidewall of the device is saturated with dangling bonds by anodic sulfidation, then a 0.2 μm thick silicon dioxide layer is deposited for passivation protection, and finally a 0.03 μm thick Al2O3 layer is deposited.

10. The method for fabricating a type-II superlattice infrared detector based on MBE growth according to claim 2, characterized in that, In step S10, the Ti layer is 200 nm thick and the Au layer is 1200 nm thick.

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