Method for growing second-class superlattice infrared detector based on MBE

Abstract

The invention relates to the field of semiconductor device design and manufacturing, and discloses a method for growing a second-class superlattice infrared detector based on MBE. A buffer layer disposed over the semiconductor substrate; the N-type lower electrode contact layer is positioned above the buffer layer; the medium-wave infrared absorption layer is positioned above the N-type lower electrode contact layer; the electron barrier layer is positioned above the medium-wave infrared absorption layer; the short-wave infrared absorption layer is positioned above the electron barrier layer; the N-type upper electrode contact layer is positioned above the short wave infrared absorption layer; the Cap layer is located above the N-type upper electrode contact layer; an upper electrode of the electrode layer is positioned above the Cap layer; the lower electrode is connected with the N-type lower electrode contact layer; and the passivation layer covers the side wall of the detector. Different absorption layers are separated by adopting the electron barrier layer, and the crosstalk effect between different wave bands is reduced, so that the false alarm rate of the detector in a complex environment is reduced, and the detector can still keep high precision in a high-interference environment due to the characteristic.

Description

Technical Field

[0001] The invention relates to the field of semiconductor device design and manufacturing, and in particular to a method for growing a second type of superlattice infrared detector based on MBE. Background Art

[0002] InAs / GaSb type II superlattice is regarded as the preferred material for the third generation of infrared focal plane detectors. In recent years, the United States, Germany, Japan and other countries have been actively promoting infrared detection technology based on this type II superlattice. The InAs / GaSb heterogeneous material system has a unique band structure. The bandgap width of InAs is smaller than the valence band offset of InAs / GaSb, so the bottom of the conduction band of InAs is below the top of the valence band of GaSb, forming a type II superlattice structure. This causes the electrons and holes to be separated in space, with the electrons confined in the InAs layer and the holes confined in the GaSb layer, and their effective bandgap width is the energy difference from the electron microband to the heavy hole microband. The mature molecular beam epitaxial growth technology of III-V compounds provides technical support for the preparation of high-performance type II superlattices. More importantly, the type II superlattice material system provides more design possibilities for the detector structure, with a bandgap adjustable from 2μm30μm, and can prepare short-wave, medium-wave, long-wave, very long-wave, dual-color band and multi-band devices.

[0003] However, the current InAs / GaSb type II superlattice detectors have insufficient detection capabilities in complex environments, resulting in a high false alarm rate. Summary of the invention

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

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: a second-type superlattice infrared detector based on MBE growth, comprising:

[0006] Semiconductor substrate: The semiconductor substrate is GaSb material;

[0007] Buffer layer: arranged on 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, and is doped to form an N-type conductive layer;

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

[0010] Electron barrier layer: located above the mid-wave infrared absorption layer, the electron barrier layer is made of AlGaAs material;

[0011] Short-wave infrared absorption layer: located above the electron barrier layer, the short-wave infrared absorption layer is an InAs / GaSb superlattice structure and is undoped;

[0012] N-type upper electrode contact layer: located above the short-wave infrared absorption layer, the N-type upper electrode contact layer is an InAs / GaSb superlattice structure, and is formed into an N-type conductive layer after doping treatment;

[0013] Cap layer: located above the N-type upper electrode contact layer. The Cap layer is made of InAs material and is doped to form the 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 to the N-type lower electrode contact layer, made of Ti / Au alloy;

[0015] Passivation layer: covers the side walls of the detector, and the passivation materials are silicon dioxide and aluminum oxide.

[0016] Preferably, a method for preparing a type II superlattice infrared detector based on MBE growth comprises the following steps:

[0017] S1: Pretreatment of GaSb substrate

[0018] The GaSb substrate is placed in the MBE growth system and first subjected to high-temperature deoxidation treatment;

[0019] S2: Growth of GaSb buffer layer

[0020] epitaxially growing a GaSb buffer layer on the pre-treated GaSb substrate;

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

[0022] On the GaSb buffer layer, grow an InAs / GaSb superlattice structure consisting of 10 layers of InAs and 10 layers of GaSb stacked alternately;

[0023] S4: Growth of mid-wave infrared absorption layer

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

[0025] S5: Growth of the electron barrier layer

[0026] In order to separate the detection areas of different wavebands, an Al.Ga.As electron barrier layer is grown on the medium-wave absorption layer;

[0027] S6: Growth of shortwave infrared absorption layer

[0028] A short-wave infrared absorption layer is grown on the electron barrier layer. The absorption layer adopts a super lattice structure of 7 layers of InAs and 7 layers of GaSb stacked alternately, and is not doped.

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

[0030] An InAs / GaSb superlattice structure is grown on top of the short-wave infrared absorption layer. The structure consists of 7 layers of InAs and 6 layers of GaSb stacked alternately.

[0031] S8: Growth of Cap Layer

[0032] Growing an InAsCap layer on 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] Ti / Au alloy was selected as the electrode material. First, a Ti layer was deposited on the device surface using electron beam evaporation technology, and then an Au layer was deposited to form an electrode structure.

[0037] Preferably, in the step S1, the specific operation is to heat the substrate to 520-550° C. and continuously treat and remove the oxide layer on the surface of the substrate at this temperature.

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

[0039] Preferably, in the 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 doping concentration of 2×10 18 cm -3 In the step S4, the thickness of the medium-wave infrared absorption layer is 2-4 μm.

[0040] Preferably, in the step S4, the thickness of the medium-wave infrared absorption layer grown on the N-type lower electrode contact layer is 2-4 μm; in the step S5, the Al 0.2 Ga 0.8 The thickness of the As electron 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 the step S7, the thickness of the InAs / GaSb superlattice structure is 0.3-0.5 μm, and this region is also doped with Si, and the doping concentration is controlled at 2×10 18 cm -3 In the step S8, the thickness of the InAsCap layer is 30 nm and the doping concentration is 2×10 18 cm -3 .

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

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

[0045] The present invention provides a method for growing a second type of superlattice infrared detector based on MBE, which has the following beneficial effects:

[0046] 1. The present invention uses an electronic barrier layer to separate different absorption layers, thereby reducing the crosstalk effect between different bands, thereby reducing the false alarm rate of the detector in a complex environment. This feature enables the detector to maintain high accuracy in a high interference environment.

[0047] 2. The present invention uses the InAs / GaSb type II superlattice structure, which can achieve efficient infrared detection. The special band structure of the type II superlattice separates electrons and holes, reduces non-radiative recombination, and thus improves the response rate and sensitivity of the detector.

[0048] 3. The present invention realizes dual-color or multi-band infrared detection by integrating absorption layers of different bands (such as medium-wave and short-wave absorption layers). The absorption layers of different bands can simultaneously detect information of multiple infrared bands, thereby improving the application range and flexibility of the detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 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 AFM schematic diagram of the present invention;

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

[0052] Figure 4 Schematic diagram of the energy band structure of the present invention.

[0053] Among them, 1. semiconductor substrate; 2. buffer layer; 3. N-type lower electrode contact layer; 4. medium-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 DESCRIPTION

[0054] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings 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.

[0055] Please see attached Figure 1 The embodiment of the present invention provides a second type of superlattice infrared detector based on MBE growth, including:

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

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

[0058] 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, and is doped to form an N-type conductive layer;

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

[0060] The electron barrier layer 5 is located above the medium-wave infrared absorption layer 4. The electron barrier layer 5 is made of AlGaAs material and is used to separate the medium-wave infrared absorption layer from the short-wave infrared absorption layer to reduce the crosstalk phenomenon between different bands.

[0061] Short-wave infrared absorption layer 6: located above the electron barrier layer 5, the short-wave infrared absorption layer 6 is an InAs / GaSb superlattice structure, is undoped, and is 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, and is formed into an N-type conductive layer after doping treatment;

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

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

[0065] The lower electrode is connected to the N-type lower electrode contact layer 7 and is made of Ti / Au alloy to form a circuit connection;

[0066] Passivation layer 10: covers the side wall of the detector. The passivation material is silicon dioxide and aluminum oxide. It is used to protect the side wall of the device and reduce the impact of the surface state on the device performance.

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

[0068] S1: Pretreatment of GaSb substrate:

[0069] The GaSb substrate is placed in the MBE growth system and first subjected to high-temperature deoxidation treatment. The specific operation is to heat the substrate to 520-550°C and continue to treat at this temperature to remove the oxide layer on the substrate surface to ensure the interface quality in the subsequent growth process.

[0070] S2: Growth of GaSb buffer layer:

[0071] On the pre-treated GaSb substrate, a 300-600nm thick GaSb buffer layer is epitaxially grown. This process is carried out using molecular beam epitaxy technology. Te is selected as the doping source of the buffer layer, and the doping concentration is controlled at 2×10 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] On the GaSb buffer layer, a 0.3-0.5 μm thick InAs / GaSb superlattice structure is grown. The structure consists of 10 layers of InAs and 10 layers of GaSb stacked alternately. Both the InAs and GaSb layers are doped with Si at a doping concentration of 2×10 18 cm -3 The superlattice structure serves as an N-type lower electrode contact layer, providing a good conductive path for subsequent electron transmission.

[0074] S4: Growth of mid-wave 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. The absorption layer also adopts an InAs / GaSb superlattice structure, and the thickness of each layer of InAs and GaSb is precisely controlled to ensure effective absorption of mid-wave infrared light.

[0076] S5: Growth of electron barrier layer:

[0077] In order to separate the detection areas of different bands, a 0.3-0.5μm thick Al.Ga.As electron barrier layer is grown on the medium-wave absorption layer. This barrier layer forms an effective barrier by adjusting the ratio of Al and Ga, reducing the crosstalk between different bands and improving the selectivity of the detector.

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

[0079] A short-wave infrared absorption layer with a thickness of 2.5-5 μm is grown on the electron barrier layer. The absorption layer adopts a superlattice structure of 7 layers of InAs and 7 layers of GaSb stacked alternately, and is not doped to maintain the intrinsic properties of the material and ensure efficient absorption of short-wave infrared light.

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

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

[0082] S8: Growth of Cap layer:

[0083] A 30nm thick InAsCap layer is grown on the N-type upper electrode contact layer with a doping concentration of 2×10 18 cm -3 The Cap layer is used to enhance the ohmic contact and ensure 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 device sidewalls are saturated with dangling bonds by anodic sulfurization, followed by the deposition of a 0.2μm thick silicon dioxide layer for passivation protection, and finally a 0.03μm thick Al2O3 layer to further improve the durability and stability of the device.

[0086] S10: Electrode fabrication:

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

[0088] Experimental Results

[0089] Epitaxially grown epitaxial wafers are 10×10μm 2 The surface roughness RMS in the range is 0.19nm, and there is an obvious step flow on the surface, indicating that the epitaxial wafer growth is good. Figure 2 .

[0090] Dark current refers to the current that exists inside electronic devices and persists even without external light exposure. This current is mainly caused by impurities, defects or thermally excited carriers, rather than being affected by external light. Figure 3 These are the test results of device current response with and without illumination. It is obvious that there is 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 the crosstalk between different bands.

[0092] Summary Conclusion

[0093] By superimposing two different medium-wave infrared detectors, detection of two different infrared bands can be achieved, which provides a guiding idea for achieving detection in more bands.

[0094] 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 type II superlattice infrared detector based on MBE growth, characterized in that: include: Semiconductor substrate (1): The semiconductor substrate (1) is GaSb material; Buffer layer (2): arranged on the semiconductor substrate (1), and 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, and is formed into an N-type conductive layer after being doped; A medium-wave infrared absorption layer (4): located above the N-type lower electrode contact layer (3), the medium-wave infrared absorption layer (4) is an InAs / GaSb superlattice structure; An electron barrier layer (5): located above the medium-wave infrared absorption layer (4), and the electron barrier layer (5) is made of AlGaAs material; Short-wave infrared absorption layer (6): located above the electron 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, and is formed into an N-type conductive layer after being doped; Cap layer (8): located above the N-type upper electrode contact layer (7), the Cap layer (8) is made of InAs material and is doped to form an 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: connected to the N-type lower electrode contact layer (3), made of Ti / Au alloy; Passivation layer (10): covers the side wall of the detector, and the passivation material is silicon dioxide and aluminum oxide.

2. A method for preparing a type II superlattice infrared detector based on MBE growth, according to the type II superlattice infrared detector based on MBE growth according to claim 1, characterized in that: The following steps are involved: S1: Pretreatment of GaSb substrate The GaSb substrate is placed in the MBE growth system and first subjected to high-temperature deoxidation treatment; S2: Growth of GaSb buffer layer (2) epitaxially growing a GaSb buffer layer (2) on the pre-treated GaSb substrate; S3: Growth of N-type lower electrode contact layer (3) On the GaSb buffer layer (2), a layer of InAs / GaSb superlattice structure is grown, wherein the structure is composed of 10 layers of InAs and 10 layers of GaSb stacked alternately; S4: Growth of mid-wave infrared absorption layer (4) A medium-wave infrared absorption layer (4) is grown on the N-type lower electrode contact layer (3), and the absorption layer also adopts an InAs / GaSb superlattice structure; S5: Growth of electron barrier layer (5) In order to separate the detection areas of different wavebands, an Al.Ga.As electron barrier layer (5) is grown on the medium wave absorption layer; S6: Growth of short-wave infrared absorption layer (6) A short-wave infrared absorption layer (6) is grown on the electron barrier layer (5), wherein the absorption layer adopts a super lattice structure in which 7 layers of InAs and 7 layers of GaSb are alternately stacked and is not doped; S7: Growth of N-type upper electrode contact layer (7) Growing an InAs / GaSb superlattice structure on the short-wave infrared absorption layer (6), the structure consisting of 7 layers of InAs and 6 layers of GaSb stacked alternately; S8: Growth of Cap layer (8) Growing an InAsCap layer (8) on 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 Ti / Au alloy was selected as the electrode material. First, a Ti layer was deposited on the device surface using electron beam evaporation technology, and then an Au layer was deposited to form an electrode structure.

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

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

5. The method for preparing a type II superlattice infrared detector based on MBE growth according to claim 2, characterized in that: In the 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 doping concentration of 2×10 18 cm -3 In the step S4, the thickness of the medium-wave infrared absorption layer (4) is 2-4 μm.

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

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

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

9. The method for preparing a type II superlattice infrared detector based on MBE growth according to claim 2, characterized in that: In the step S9, first, the device sidewall is subjected to dangling bond saturation treatment by an anodic sulfurization method, and then a 0.2 μm thick silicon dioxide layer is deposited for passivation protection, and finally a 0.03 μm thick Al2O3 is deposited.

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

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