A recessed groove type group iii nitride heterojunction high-speed photodetector and a preparation method thereof
By using a grooved group III nitride heterojunction structure and metal self-aligned etching technology, the problems of high dark current and slow response of traditional photodetectors have been solved, and a photodetector with low dark current, high gain and fast response has been fabricated and applied in multiple fields.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANJING UNIV
- Filing Date
- 2024-12-25
- Publication Date
- 2026-06-23
AI Technical Summary
Traditional N-channel or P-channel photoconductive group III nitride photodetectors suffer from high dark current and slow response speed, which limits their development in various application fields.
A grooved group III nitride heterojunction structure is adopted, and a heterostructure with negative or positive polarization charge is formed by using unintentionally doped channel absorption layer and barrier layer. Ohmic contact electrodes are prepared by metal self-aligned etching technology to avoid heterojunction polarization caused by photolithography and improve response speed.
It achieves low dark current, high gain and fast response photodetector, suitable for ultraviolet and visible light detection, and can be applied in missile early warning, environmental monitoring, flame alarm, medical imaging, ultraviolet metrology, visible light communication, underwater optical communication and autonomous driving.
Smart Images
Figure CN122269818A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a grooved group III nitride heterojunction high-speed photodetector and its fabrication method, belonging to the field of semiconductor optoelectronic device technology. Background Technology
[0002] Photoelectric detection technology has important applications in both military and civilian fields. Research and breakthroughs in wide-bandgap group III nitride semiconductor materials (including GaN, AlGaN, and InGaN) have driven the development of various photoelectric detection devices. Group III nitride photodetectors can detect wavelengths in both the ultraviolet and visible light ranges. Ultraviolet detection is mainly used in missile early warning, environmental monitoring, flame alarms, medical imaging, and ultraviolet metrology; visible light detection is mainly used in visible light communication, underwater optical communication, cameras, and autonomous driving.
[0003] Photoconductive detectors based on group III nitride semiconductors have attracted widespread attention due to their simplest device architecture (only two ohmic contacts) and high internal gain. However, the development of traditional N-channel or P-channel photoconductive detectors is hampered by two key problems: high dark current caused by channel doping and slow response times of milliseconds or seconds, which severely restrict the development and application of this type of detector. Therefore, how to fabricate high-performance photoconductive detectors with low dark current, high gain, and fast response remains an urgent need in various application fields. Summary of the Invention
[0004] The purpose of this invention is to provide a grooved group III nitride heterojunction high-speed photodetector, which has the effects of low dark current, high gain and fast response.
[0005] The technical solution adopted in this invention is as follows:
[0006] A grooved group III nitride heterojunction high-speed photodetector includes: a substrate; a buffer layer, a channel absorption layer, and a barrier layer grown sequentially from bottom to top on the substrate; ohmic contact electrode layers at both ends of the barrier layer; and a groove exposing the channel absorption layer between the two ohmic contact electrode layers. The channel absorption layer and the barrier layer are both made of unintentionally doped group III nitrides, and the channel absorption layer and the barrier layer are heterostructures that generate negative or positive polarization charges at the interface.
[0007] Preferably, the system further includes a spacer layer located between the channel absorber layer and the barrier layer. This spacer layer is made of unintentionally doped AlN and has a thickness of 0-2 nm. The spacer layer enhances the polarization of the barrier / channel absorber layer.
[0008] Preferably, the substrate is any one of a Si substrate, a sapphire substrate, a silicon carbide substrate, or a GaN self-supporting substrate.
[0009] Preferably, the buffer layer is a high-resistivity buffer layer, which is a superlattice structure composed of GaN, AlGaN, AlN, or a combination thereof, and the resistivity of the buffer layer is 10. 5 The thickness is above Ω·cm, the doping element is carbon or iron, and the thickness is 100nm~20μm.
[0010] Preferably, the heterostructure of the barrier layer / channel absorber layer is Al. x Ga 1-x N / Al y Ga 1-y N、In x Ga 1-x N / In y Ga 1-y N or Al x In 1-x N / GaN; the absorption layer thickness ranges from 100 nm to 5 μm, and the barrier layer thickness ranges from 5 nm to 50 nm.
[0011] Preferably, the Al x Ga 1-x N / Al y Ga 1-y N、In x Ga 1-x N / In y Ga 1-y N or Al x In 1-x Negative or positive polarization charges are generated at the N / GaN interface, wherein 0≤x≤1, 0≤y≤1, and x≠y.
[0012] Preferably, the structure of the electrode layer is Ti / Al / Ni / Au, Ti / Al / Ti / Au, Ti / Al / Mo / Au, V / Al / V / Au, V / Al / Ti / Au, Ti / Al / Ti, Ti / Al / Ti / TiN, or a Ni / Au alloy.
[0013] The fabrication method of the above-mentioned grooved group III nitride heterojunction high-speed photodetector includes the following steps:
[0014] S1. A buffer layer, a channel absorption layer, and a barrier layer are sequentially grown on the substrate;
[0015] S2. Spin-coat a layer of photoresist on the surface of the barrier layer, and remove part of the photoresist through pre-baking, exposure and development to obtain the electrode structure. Then, deposit a metal alloy by electron beam evaporation and then peel off the metal electrode.
[0016] S3. Using a metal self-alignment method, reactive ion etching is performed on the area between the two metal electrodes to expose the channel absorption layer, followed by annealing in a rapid annealing furnace to form an ohmic contact electrode layer; or the ohmic contact electrode layer is first formed by annealing, and then reactive ion etching is performed on the area between the two metal electrodes using a metal self-alignment method to expose the channel absorption layer.
[0017] S4. Deposit SiO2 or SiN on the device surface x Alternatively, Al2O3 can form a passivation layer to protect the device;
[0018] S5. Use a reactive ion etching machine to remove the passivation layer on the surface of the ohmic contact electrode.
[0019] Preferably, in step S1, a buffer layer, a channel absorption layer, a spacer layer, and a barrier layer are grown sequentially on the substrate.
[0020] Preferably, the annealing conditions in step S3 are: annealing at 850°C in a N2 atmosphere for 30 seconds.
[0021] The beneficial effects of this invention are:
[0022] This invention uses an unintentionally doped nitride layer as the conductive channel of a photoconductive detector, which can effectively reduce dark current while improving device response speed. Ohmic contact electrodes are fabricated using a heterostructure that generates negative or positive polarization charges at the interface between the absorption layer and the barrier layer, solving the problem of difficulty in forming ohmic contacts with unintentionally doped nitride layers. Groove etching is performed using a metal self-alignment method, avoiding the capture of photogenerated carriers by heterojunction polarization caused by photolithography, further improving the device response speed. Thus, a high-performance photoconductive detector with low dark current, high gain, and fast response is fabricated, showing great application potential. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of the structure of the groove-type group III nitride heterojunction high-speed photoconductive detector of the present invention.
[0024] Figure 2 This is a schematic diagram of the device structure of the groove-type group III nitride heterojunction high-speed photoconductive detector of Example 1.
[0025] Figure 3 This is a schematic diagram of the fabrication process of the groove-type group III nitride heterojunction high-speed photoconductive detector device in Example 1.
[0026] Figure 4 This is a performance diagram of the grooved group III nitride heterojunction high-speed photoconductive detector device IV prepared in Example 1.
[0027] Figure 5This is a response time performance diagram of the groove-type group III nitride heterojunction high-speed photoconductive detector device prepared in Example 1. Detailed Implementation
[0028] The present invention will be further described below with reference to the embodiments, but the description of the embodiments does not limit the scope of protection of the present invention in any way.
[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. Furthermore, while this document provides examples of parameters containing specific values, it should be understood that the parameters need not be exactly equal to the corresponding values, but can approximate the corresponding values within acceptable error tolerances or design constraints. Directional terms mentioned in the embodiments, such as “up,” “down,” “front,” “back,” “left,” “right,” etc., are only for reference to the accompanying drawings. Therefore, the directional terms used are for illustrative purposes and not for limiting the scope of protection of this invention.
[0030] Unless otherwise specified, all substances or instruments used in the following examples can be obtained from conventional commercial sources.
[0031] Example 1
[0032] like Figure 1-2 As shown, this embodiment discloses a high-speed photoconductive detector based on a metal self-aligned groove-type group III nitride heterojunction, which mainly includes a substrate layer, a high resistivity buffer layer, a channel absorption layer, a spacer layer, a barrier layer, and an ohmic contact electrode layer arranged sequentially from bottom to top.
[0033] The substrate is a Si substrate;
[0034] The high resistivity buffer layer is a GaN structure, doped with carbon, and has a thickness of 4.7 μm.
[0035] The channel absorption layer is an unintentionally doped GaN layer with a thickness of 300 nm.
[0036] The spacer layer is an unintentionally doped AlN layer with a thickness of 1 nm.
[0037] The barrier layer is an unintentionally doped AlGaN layer with a thickness of 21 nm and an Al content of 25%.
[0038] The ohmic contact electrode layer is formed by a rapid thermal annealing process of 20 / 120 / 50 / 50nm thick Ti / Au / Ti / Au multilayer metals at 850℃ in a N2 atmosphere for 30s. A groove is etched into the channel absorption layer between the two ohmic contact electrode layers.
[0039] like Figure 3 As shown, the above-mentioned method for fabricating a high-speed photoconductive detector based on a metal self-alignment groove-type group III nitride heterojunction includes the following steps:
[0040] (1) A layer of photoresist is spin-coated on the surface of the barrier layer. After pre-baking, exposure and development, part of the photoresist is removed to obtain the electrode structure at both ends. A Ti / Au / Ti / Au metal alloy with a thickness of 20 / 120 / 50 / 50nm is deposited by electronic evaporation. Then the metal electrodes are peeled off.
[0041] (2) Reactive ion etching is performed between two metal electrodes using a metal self-alignment method to expose the channel absorption layer. Then, the electrode is annealed in a rapid annealing furnace at 850°C and N2 atmosphere for 30 seconds to form an ohmic contact electrode. Alternatively, an ohmic contact electrode can be formed by annealing in a conditional furnace at 850°C and N2 atmosphere for 30 seconds. Then, reactive ion etching is performed between two metal electrodes using a metal self-alignment method to expose the channel absorption layer. This ensures that only the channel absorption layer is the photoresponse region, thereby achieving high gain and fast response.
[0042] (3) Deposit SiO2 or SiN on the device surface x Alternatively, Al2O3 can form a passivation layer to protect the device;
[0043] (4) Remove the passivation layer on the surface of the ohmic contact electrode for subsequent electrical testing.
[0044] The IV performance of the device in Example 1 was tested, and the results are as follows: Figure 4 As shown, the dark current is very low, at 40 fA. The response time performance of the device in Example 1 was tested, and the results are as follows... Figure 5 As shown, the response time can reach the nanosecond level.
[0045] Example 2
[0046] This embodiment discloses a high-speed photoconductive detector based on a groove-type group III nitride heterojunction with metal self-alignment, which mainly includes a substrate layer, a high resistivity buffer layer, a channel absorption layer, a spacer layer, a barrier layer, and an ohmic contact electrode layer arranged sequentially from bottom to top.
[0047] The substrate is a Si substrate;
[0048] The high resistivity buffer layer is an AlGaN structure, doped with carbon, and has a thickness of 4.7 μm.
[0049] The channel absorption layer is an unintentionally doped AlGaN layer with a thickness of 200 nm and an Al composition of 40%.
[0050] The spacer layer is an unintentionally doped AlN layer with a thickness of 1 nm.
[0051] The barrier layer is an unintentionally doped AlGaN layer with a thickness of 15 nm and an Al composition of 65%.
[0052] The ohmic contact electrode layer is formed by a multilayer metal of V (15nm) / Al (100nm) / V (20nm) / Au (80nm) through a rapid thermal annealing process at 870℃ in a N2 atmosphere for 60s. A groove is etched into the channel absorption layer between the two ohmic contact electrode layers.
[0053] The device fabrication steps in this embodiment are largely the same as those in Embodiment 1, with the only difference being:
[0054] The metal alloy in (1) is V(15nm) / Al(100nm) / V(20nm) / Au(80nm);
[0055] (2) The annealing conditions are 870℃ and rapid thermal annealing in N2 atmosphere for 60s.
[0056] Example 3
[0057] This embodiment discloses a high-speed photoconductive detector based on a groove-type group III nitride heterojunction with metal self-alignment, which mainly includes a substrate layer, a high resistivity buffer layer, a channel absorption layer, a barrier layer, and an ohmic contact electrode layer arranged sequentially from bottom to top.
[0058] The substrate is a Si substrate;
[0059] The high resistivity buffer layer is an AlGaN / GaN superlattice structure, doped with carbon, and has a thickness of 4.7 μm.
[0060] The channel absorption layer is an unintentionally doped InGaN layer with a thickness of 400 nm and an In composition of 15%.
[0061] The barrier layer is an unintentionally doped GaN layer with a thickness of 21 nm.
[0062] The ohmic contact electrode layer is formed by thermal annealing of a 20 / 120 / 50 / 50 nm thick Ti / Au / Ti / Au multilayer metal at 800 °C for 30 seconds in a N2 atmosphere. A groove etched into the channel absorption layer is provided between the two ohmic contact electrode layers.
[0063] The device fabrication steps in this embodiment are largely the same as those in Embodiment 1, with the only difference being:
[0064] (2) The annealing conditions are 800℃ and rapid thermal annealing in N2 atmosphere for 30s.
[0065] Example 4
[0066] This embodiment discloses a high-speed photoconductive detector based on a groove-type group III nitride heterojunction with metal self-alignment, which mainly includes a substrate layer, a high resistivity buffer layer, a channel absorption layer, a spacer layer, a barrier layer, and an ohmic contact electrode layer arranged sequentially from bottom to top.
[0067] The substrate is a Si substrate;
[0068] The high resistivity buffer layer is an AlGaN structure, doped with carbon, and has a thickness of 4.7 μm.
[0069] The channel absorption layer is an unintentionally doped GaN layer with a thickness of 300 nm.
[0070] The spacer layer is an unintentionally doped AlN layer with a thickness of 1 nm.
[0071] The barrier layer is an unintentionally doped AlInN layer with a thickness of 15 nm and an Al composition of 82%.
[0072] The ohmic contact electrode layer is formed by thermal annealing of a 20 / 120 / 50 / 50 nm thick Ti / Au / Ni / Au multilayer metal at 850 °C for 30 seconds in a N2 atmosphere. A groove etched into the channel absorption layer is provided between the two ohmic contact electrode layers.
[0073] The device fabrication steps in this embodiment are largely the same as those in Embodiment 1, with the only difference being:
[0074] (1) The metal alloy in the figure is Ti / Au / Ni / Au with a thickness of 20 / 120 / 50 / 50nm;
[0075] Example 5
[0076] This embodiment discloses a groove-type group III nitride heterojunction high-speed photoconductive detector based on metal self-alignment, the structure of which includes:
[0077] A Si substrate;
[0078] A high resistivity buffer GaN layer grown on a substrate;
[0079] An unintentionally doped AlGaN barrier layer grown on a GaN layer serves as a channel absorption layer, with a thickness of 200 nm and an Al composition of 40%.
[0080] An unintentionally doped GaN layer with a thickness of 15 nm is grown on an AlGaN barrier layer.
[0081] The ohmic contact electrode layer is formed by thermal annealing of a 20 / 20nm thick Ni / Au multilayer metal at 800℃ for 30s in a N2 atmosphere. A groove etched into the channel absorption layer is provided between the two ohmic contact electrode layers.
[0082] The device fabrication steps in this embodiment are largely the same as those in Embodiment 1, with the only difference being:
[0083] (1) is a Ni / Au alloy with a thickness of 20 / 20 nm.
[0084] (2) The annealing conditions are 800℃ and rapid thermal annealing in N2 atmosphere for 30s.
[0085] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention. For better illustration of the embodiments, some parts in the drawings may be omitted or scaled, and do not represent the actual dimensions of the devices.
Claims
1. A grooved group III nitride heterojunction high-speed photodetector, characterized in that, Its structure includes: a substrate, a buffer layer, a channel absorption layer, and a barrier layer grown sequentially from bottom to top on the substrate, ohmic contact electrode layers respectively provided at both ends of the barrier layer, and a groove exposing the channel absorption layer between the two ohmic contact electrode layers. The channel absorption layer and the barrier layer are both made of unintentionally doped group III nitrides, and the channel absorption layer and the barrier layer are heterostructures that generate negative or positive polarization charges at the interface.
2. The grooved group III nitride heterojunction high-speed photodetector according to claim 1, characterized in that, It also includes a spacer layer located between the channel absorber layer and the barrier layer, which is made of unintentionally doped AlN and has a thickness of 0-2 nm.
3. The grooved group III nitride heterojunction high-speed photodetector according to claim 1 or 2, characterized in that, The substrate is any one of Si substrate, sapphire substrate, silicon carbide substrate, and GaN self-supporting substrate.
4. The grooved group III nitride heterojunction high-speed photodetector according to claim 1 or 2, characterized in that, The buffer layer is a superlattice structure composed of GaN, AlGaN, AlN, or combinations thereof, and the resistivity of the buffer layer is 10. 5 The thickness is above Ω·cm, the doping element is carbon or iron, and the thickness is 100nm~20μm.
5. The grooved group III nitride heterojunction high-speed photodetector according to claim 1 or 2, characterized in that, The heterostructure of the barrier layer / channel absorption layer is Al. x Ga 1-x N / Al y Ga 1-y N、In x Ga 1-x N / In y Ga 1-y N or Al x In 1-x N / GaN; the absorption layer thickness ranges from 100 nm to 5 μm, and the barrier layer thickness ranges from 5 nm to 50 nm.
6. The grooved group III nitride heterojunction high-speed photodetector according to claim 5, characterized in that, The Al x Ga 1-x N / Al y Ga 1-y N、In x Ga 1-x N / In y Ga 1-y N or Al x In 1-x Negative or positive polarization charges are generated at the N / GaN interface, wherein 0≤x≤1, 0≤y≤1, and x≠y.
7. The grooved group III nitride heterojunction high-speed photodetector according to claim 1 or 2, characterized in that, The electrode layer has a structure of Ti / Al / Ni / Au, Ti / Al / Ti / Au, Ti / Al / Mo / Au, V / Al / V / Au, V / Al / Ti / Au, Ti / Al / Ti, Ti / Al / Ti / TiN, or Ni / Au alloy.
8. The method for fabricating a grooved group III nitride heterojunction high-speed photodetector according to any one of claims 1-7, characterized in that... The steps include: S1. A buffer layer, a channel absorption layer, and a barrier layer are sequentially grown on the substrate; S2. Spin-coat a layer of photoresist on the surface of the barrier layer, and remove part of the photoresist through pre-baking, exposure and development to obtain the electrode structure. Then, deposit a metal alloy by electron beam evaporation and then peel off the metal electrode. S3. Using a metal self-alignment method, reactive ion etching is performed on the area between the two metal electrodes to expose the channel absorption layer, followed by annealing in a rapid annealing furnace to form an ohmic contact electrode layer; or the ohmic contact electrode layer is first formed by annealing, and then reactive ion etching is performed on the area between the two metal electrodes using a metal self-alignment method to expose the channel absorption layer. S4. Deposit SiO2 or SiN on the device surface x Alternatively, Al2O3 can form a passivation layer to protect the device; S5. Use a reactive ion etching machine to remove the passivation layer on the surface of the ohmic contact electrode.
9. The preparation method according to claim 8, characterized in that, In step S1, a buffer layer, a channel absorption layer, a spacer layer, and a barrier layer are grown sequentially on the substrate.
10. The preparation method according to claim 8 or 9, characterized in that, The annealing conditions in step S3 are: annealing at 850℃ in a N2 atmosphere for 30 seconds.