A full-duplex visible light communication system and a method of manufacturing the same

Abstract

The application discloses a full-duplex visible light communication system and a preparation method thereof, and relates to the field of optical communication.The communication system comprises a body which is divided into a transmitting area, a straight waveguide area and a photodetecting area; a first AlGaN barrier layer is grown on the top of the body in the transmitting area; a first p-type GaN layer, a source electrode and a gate electrode are grown on the first AlGaN barrier layer; a film layer and a drain electrode are grown on the first p-type GaN layer; a second AlGaN barrier layer is grown on the top of the body in the photodetecting area; a second p-type GaN layer and a cathode are grown on the second AlGaN barrier layer; and an anode is grown on the second p-type GaN layer.The application embeds a Micro-LED comprising a p-type GaN layer in the drain electrode of a driving transistor, realizes the monolithic integration of the driving transistor and the Micro-LED, solves the problem of low modulation bandwidth of the visible light communication system, and improves the performance of the visible light communication system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical communication, in particular to a full-duplex visible light communication system and a preparation method thereof. BACKGROUND

[0002] Visible light communication technology has good application prospects in indoor high-speed communication and underwater communication scenarios. The traditional visible light communication system transmits end adopts a silicon-based CMOS circuit to drive a gallium nitride-based micro-LED light source, which has problems such as parasitic capacitance introduced by heterojunction bonding process restricting switching speed, and the silicon-based CMOS device can provide limited driving current in a unit area. The high electron mobility transistor (HEMT) based on gallium nitride epitaxy has the advantages of high switching speed and large driving current at the same time, so if the gallium nitride-based transistor is monolithically integrated with the Micro-LED, the modulation bandwidth of the visible light communication system and the luminous intensity of the Micro-LED display system can be improved at the same time. At present, it is impossible to monolithically integrate the gallium nitride-based transistor with the Micro-LED, and the modulation bandwidth of the visible light communication system is low, and the performance of the visible light communication system needs to be improved. SUMMARY

[0003] Based on this, the embodiments of the present application provide a full-duplex visible light communication system and a preparation method thereof to solve the problem of low modulation bandwidth of the visible light communication system and improve the performance of the visible light communication system.

[0004] To achieve the above-mentioned purpose, the present application provides the following scheme:

[0005] A full-duplex visible light communication system, comprising: a body; the body is divided into a transmitting area, a straight waveguide area and a photoelectric detection area from left to right in sequence;

[0006] The top of the body in the transmitting area grows a first AlGaN barrier layer; a first two-dimensional electron gas layer is generated at the interface between the body in the transmitting area and the first AlGaN barrier layer; a first p-type GaN layer, a source electrode and a gate electrode are grown on the first AlGaN barrier layer; a thin film layer is grown on the first p-type GaN layer; a drain electrode is grown on the thin film layer;

[0007] The top of the body in the photoelectric detection area grows a second AlGaN barrier layer; a second two-dimensional electron gas layer is generated at the interface between the body in the photoelectric detection area and the second AlGaN barrier layer; a second p-type GaN layer and a cathode are grown on the second AlGaN barrier layer; an anode is grown on the second p-type GaN layer;

[0008] The body in the emission area, the first AlGaN barrier layer and the first two-dimensional electron gas layer constitute a driving transistor; the source, the gate and the drain serve as electrodes of the driving transistor; the first two-dimensional electron gas layer, the first AlGaN barrier layer, the first p-type GaN layer and the thin film layer constitute a Micro-LED; the drain serves as an anode of the Micro-LED, and the first two-dimensional electron gas layer serves as a cathode of the Micro-LED; the driving transistor is used for driving the Micro-LED to emit light.

[0009] Optionally, the body comprises a substrate and, sequentially from bottom to top on the substrate, a buffer layer, an intrinsic GaN layer and an InGaN quantum well layer.

[0010] Optionally, the thin film layer is a thin Ni / Au layer.

[0011] Optionally, the substrate is a silicon substrate.

[0012] Optionally, the substrate is a sapphire substrate, a silicon carbide substrate or a gallium nitride substrate.

[0013] Optionally, the buffer layer is a gallium nitride layer doped with iron or carbon.

[0014] Optionally, the buffer layer is an AlGaN / GaN superlattice structure.

[0015] The application further provides a preparation method of a full-duplex visible light communication system, comprising:

[0016] The body is sequentially divided from left to right into an emission area, a straight waveguide area and a photodetection area;

[0017] An AlGaN barrier layer and a p-type GaN layer are sequentially grown from bottom to top on the body;

[0018] The AlGaN barrier layer and the p-type GaN layer in the straight waveguide area are etched to achieve mesa isolation, a first AlGaN barrier layer is formed in the emission area, and a second AlGaN barrier layer is formed in the photodetection area;

[0019] Part of the p-type GaN layer on the first AlGaN barrier layer is etched to obtain a first p-type GaN layer, and part of the p-type GaN layer on the second AlGaN barrier layer is etched to obtain a second p-type GaN layer;

[0020] An ohmic contact metal is evaporated on the first AlGaN barrier layer, the second p-type GaN layer and the second AlGaN barrier layer to obtain a source in the emission area, an anode in the photodetection area and a cathode in the photodetection area;

[0021] depositing a thin film layer on the first p-type GaN layer;

[0022] evaporating Schottky contact metal on the first AlGaN barrier layer and the thin film layer to obtain the gate and the drain in the emission region.

[0023] Optionally, evaporating ohmic contact metal on the first AlGaN barrier layer, the second p-type GaN layer and the second AlGaN barrier layer to obtain the source in the emission region, the anode in the photoelectric detection region and the cathode in the photoelectric detection region, specifically comprising:

[0024] carrying out acid treatment on the device surface of the completed mesa isolation to obtain a treated device;

[0025] evaporating ohmic contact metal on the first AlGaN barrier layer, the second p-type GaN layer and the second AlGaN barrier layer in the treated device by using an electron evaporation process and carrying out annealing treatment at a set temperature to form the source in the emission region, the anode in the photoelectric detection region and the cathode in the photoelectric detection region.

[0026] Optionally, depositing a thin film layer on the first p-type GaN layer, specifically comprising:

[0027] depositing thin Ni / Au on the first p-type GaN layer by using an electron beam evaporation process to form the thin film layer and carrying out annealing treatment at a set temperature on the thin film layer to make the thin film layer form ohmic contact with the first p-type GaN layer.

[0028] According to the embodiments of the present application, the following technical effects are provided:

[0029] The embodiment of the present application provides a full-duplex visible light communication system and a preparation method thereof, a top of a body in a transmitting area is grown with a first AlGaN barrier layer; the first AlGaN barrier layer is grown with a first p-type GaN layer, a source electrode and a gate electrode; the first p-type GaN layer is grown with a film layer and a drain electrode; a top of a body of a photoelectric detection area is grown with a second AlGaN barrier layer; the second AlGaN barrier layer is grown with a second p-type GaN layer and a cathode; the second p-type GaN layer is grown with an anode. The body in the transmitting area, the first AlGaN barrier layer and the first two-dimensional electron gas layer of the present application constitute a driving transistor, the first two-dimensional electron gas layer, the first AlGaN barrier layer, the first p-type GaN layer and the film layer constitute a Micro-LED, the drain electrode of the driving transistor is embedded with the Micro-LED, the drain electrode of the driving transistor and the anode of the Micro-LED are integrated, and the two-dimensional electron gas layer replaces the cathode of the Micro-LED, the integration of the driving transistor and the Micro-LED is realized, the parasitic elements caused by the metal interconnection are minimized, the modulation bandwidth is improved, the problem of low modulation bandwidth of the visible light communication system is solved, and the performance of the visible light communication system is improved. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings described in the following only constitute some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative labor.

[0031] Figure 1 A structural diagram of the full-duplex visible light communication system provided by the embodiment of the present application is provided.

[0032] Figure 2 A flowchart of the preparation method of the full-duplex visible light communication system provided by the embodiment of the present application is provided.

[0033] Symbol explanation:

[0034] Substrate-1, transmitting area-2, straight waveguide area-3, photoelectric detection area-4, buffer layer-5, intrinsic GaN layer-6, InGaN quantum well layer-7, first AlGaN barrier layer-8, second AlGaN barrier layer-9, first two-dimensional electron gas-10, second two-dimensional electron gas-11, drain electrode area of the transmitting area-21, first p-type GaN layer-22, drain electrode-23, source electrode-24, gate electrode-25, film layer-26, anode-41, cathode-42, second p-type GaN layer-43. DETAILED DESCRIPTION

[0035] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of the present application.

[0036] The present application provides a gallium nitride-based high electron mobility transistor (HEMT) as a transmitting device with higher switching frequency and driving current, and designs an in-plane full-duplex visible light communication system based on a single-chip gallium nitride optical interconnection by fusing the epitaxial features of the driving device, the light-emitting device, the straight waveguide and the photodetector, to solve the problem of low modulation bandwidth of the existing visible light communication system and improve the performance of the visible light communication system.

[0037] In order to make the above-mentioned purposes, features and advantages of the present application more apparent and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0038] Embodiment One

[0039] The full-duplex visible light communication system of the present embodiment is realized based on a single-chip gallium nitride optical interconnection. Referring to Figure 1 , the full-duplex visible light communication system comprises a body; the body is divided into a transmitting area 2, a straight waveguide area 3 and a photodetection area 4 from left to right.

[0040] The top of the body in the transmitting area 2 grows a first AlGaN barrier layer 8; a first two-dimensional electron gas layer 10 is generated at the interface between the body in the transmitting area 2 and the first AlGaN barrier layer 8; a first p-type GaN layer 22, a source 24 and a gate 25 are grown on the first AlGaN barrier layer 8; a thin film layer 26 is grown on the first p-type GaN layer 22; a drain 23 is grown on the thin film layer 26.

[0041] The top of the body in the photodetection area 4 grows a second AlGaN barrier layer 9; a second two-dimensional electron gas layer 11 is generated at the interface between the body in the photodetection area 4 and the second AlGaN barrier layer 9; a second p-type GaN layer 43 and a cathode 42 are grown on the second AlGaN barrier layer 9; an anode 41 is grown on the second p-type GaN layer 43.

[0042] The body in the emission region 2, the first AlGaN barrier layer 8 and the first two-dimensional electron gas layer 10 constitute a driving transistor; the source 24, the gate 25 and the drain 23 serve as electrodes of the driving transistor; the first two-dimensional electron gas layer 10, the first AlGaN barrier layer 8, the first p-type GaN layer 22 and the thin film layer 26 constitute a Micro-LED; the drain 23 serves as an anode of the Micro-LED, and the first two-dimensional electron gas layer 10 serves as a cathode of the Micro-LED; the driving transistor is used to drive the Micro-LED to emit light. The drain region 21 of the emission region 2 in the embodiment realizes the monolithic integration of the driving transistor and the Micro-LED. The driving transistor can be a high electron mobility transistor (HEMT). That is, the Micro-LED can be embedded in the drain 23 of the high electron mobility transistor (HEMT) to realize the integration of the two, thereby minimizing the parasitic elements caused by metal interconnection, improving the modulation bandwidth, solving the problem of low modulation bandwidth of the visible light communication system, and improving the performance of the visible light communication system.

[0043] In one example, the thin film layer 26 is a thin Ni / Au layer. The thin Ni / Au layer is located between the drain 23 and the first p-type GaN layer 22, and forms an ohmic contact with the first p-type GaN layer 22 through high-temperature annealing.

[0044] The body is further described below.

[0045] The body includes a substrate 1, a buffer layer 5, an intrinsic GaN layer 6 and an InGaN quantum well layer 7 grown on the substrate 1 from bottom to top. The straight waveguide region 3 in the embodiment is an InGaN straight waveguide region.

[0046] The substrate 1 is a silicon substrate (Silicon), a sapphire substrate (Sappire), a silicon carbide substrate (SiC) or a self-supporting gallium nitride substrate, and serves as a support for the entire structure.

[0047] The buffer layer 5 is located on the substrate 1. The buffer layer 5 is used to release stress and filter dislocations to obtain a perfect crystal quality. The buffer layer 5 can be a gallium nitride layer doped with iron (Fe) or carbon (C) or an AlGaN / GaN superlattice structure.

[0048] The intrinsic GaN layer 6 is located above the buffer layer 5, the InGaN quantum well layer 7 is located above the intrinsic GaN layer 6, the first AlGaN barrier layer 8 is located above the InGaN quantum well layer 7 and generates a two-dimensional electron gas (2DEG) on the side close to the InGaN quantum well layer 7 at the interface between the first AlGaN barrier layer 8 and the InGaN quantum well layer 7 through piezoelectric polarization and spontaneous polarization effect, that is, a first two-dimensional electron gas 10 is obtained. The second AlGaN barrier layer 9 is located above the InGaN quantum well layer 7 and generates a two-dimensional electron gas (2DEG) on the side close to the InGaN quantum well layer 7 at the interface between the second AlGaN barrier layer 9 and the InGaN quantum well layer 7 through piezoelectric polarization and spontaneous polarization effect, that is, a second two-dimensional electron gas 11 is obtained.

[0049] The full-duplex visible light communication system of the embodiment is a full-duplex visible light communication system integrating a driving transistor, a light source, a waveguide and a photodetector in one piece, which is based on an epitaxial structure similar to a p-GaN cap layer driving transistor (such as a HEMT), and a layer of InGaN quantum well is inserted between AlGaN and GaN, which simultaneously serves as an active layer of a light source (such as a Micro-LED), a channel layer of a driving transistor, a straight waveguide layer and a photoelectric conversion layer of a detector. The InGaN / GaN quantum well diode device can realize the dual functions of a Micro-LED and a detector, and the two diode devices respectively serving as a Micro-LED and a detector are integrated through an InGaN straight waveguide to realize an on-chip high-speed visible light communication (VLC) system. The anode of the Micro-LED and the drain of the driving transistor are integrated, and the 2DEG (two-dimensional electron gas) is used to replace the cathode of the Micro-LED, which can minimize the parasitic elements caused by metal interconnection, and thus improve the modulation bandwidth of the VLC system, solving the problem of low modulation bandwidth of the existing visible light communication system and improving the performance of the visible light communication system.

[0050] Embodiment two

[0051] The embodiment provides a preparation method of a full-duplex visible light communication system, which comprises the following steps:

[0052] The body is sequentially divided into an emission area 2, a straight waveguide area 3 and a photodetection area 4 from left to right.

[0053] An AlGaN barrier layer and a p-type GaN layer are sequentially grown on the body from bottom to top.

[0054] 1) Etching the AlGaN barrier layer and the p-type GaN layer in the straight waveguide area 3 to realize mesa isolation, forming a first AlGaN barrier layer 8 in the emission area 2 and a second AlGaN barrier layer 9 in the photodetection area 4.

[0055] 2) etching part of the p-type GaN layer on the first AlGaN barrier layer 8 to obtain a first p-type GaN layer 22, and etching part of the p-type GaN layer on the second AlGaN barrier layer 9 to obtain a second p-type GaN layer 43.

[0056] 3) evaporating ohmic contact metal on the first AlGaN barrier layer 8, the second p-type GaN layer 43 and the second AlGaN barrier layer 9 to obtain the source 24 in the emission region 2, the anode 41 in the photodetection region 4 and the cathode 42 in the photodetection region 4. Specifically:

[0057] The device surface on which the mesa isolation is completed is subjected to acid treatment to obtain a treated device; an ohmic contact metal is evaporated on the first AlGaN barrier layer 8, the second p-type GaN layer 43 and the second AlGaN barrier layer 9 in the treated device by using an electron evaporation process, and an annealing treatment at a set temperature is performed to form the source 24 in the emission region 2, the anode 41 in the photodetection region 4 and the cathode 42 in the photodetection region 4.

[0058] 4) depositing a thin film layer 26 on the first p-type GaN layer 22. Specifically:

[0059] A thin Ni / Au is deposited on the first p-type GaN layer 22 by using an electron beam evaporation process to form the thin film layer 26, and an annealing treatment at a set temperature is performed on the thin film layer 26 to form an ohmic contact between the thin film layer 26 and the first p-type GaN layer 22.

[0060] 5) evaporating a Schottky contact metal on the first AlGaN barrier layer 8 and the thin film layer 26 to obtain the gate 25 and the drain 23 in the emission region 2.

[0061] In practical applications, referring to Figure 2 A process for preparing a full-duplex visible light communication system is as follows:

[0062] Step 1: preparing an epitaxial wafer. An epitaxial wafer having a substrate, a buffer layer, an intrinsic GaN layer, an InGaN quantum well layer, an AlGaN barrier layer and a p-type GaN layer is selected, and the epitaxial wafer is cleaned.

[0063] Step 2: mesa isolation.

[0064] Step 3: etching the p-type GaN. The p-type GaN layer in the emission region and the p-type GaN layer in the photodetection region are etched.

[0065] Step 4: etching the p-type GaN and the AlGaN. The p-type GaN layer and the AlGaN barrier layer in the straight waveguide region are etched.

[0066] Step 5: Surface treatment. Surface treatment (acid treatment: HCl, H2SO4+H2O2, BOE) is performed on the device with completed mesa isolation.

[0067] Step 6: Source, anode and cathode metal deposition, forming ohmic contact. Electron beam evaporation process is used to evaporate ohmic contact metal (e.g., Ti / Al / Ni / Au or Ti / Al / Ti / Au) on the source region, anode region and cathode region, and high-temperature annealing is performed to form the source, anode and cathode.

[0068] Step 8: Deposition of thin Ni / Au, forming ohmic contact with p-type GaN. Electron beam evaporation process is used to deposit thin Ni / Au on the p-type GaN layer after etching the emission region, and high-temperature annealing is performed to form ohmic contact with the p-type GaN layer.

[0069] Step 9: Gate and drain metal deposition. Schottky contact metal Ni / Au is evaporated on the gate region and drain region to form the gate and drain.

[0070] The preparation method of the embodiment is used to prepare an in-plane full-duplex visible light communication system based on a monolithic gallium nitride optical interconnection, and the emission region is equivalent to a drain embedded with a driving transistor of a Micro-LED, which can minimize the parasitic elements caused by metal interconnection. For the InGaN straight waveguide region, the p-GaN and AlGaN above the InGaN are etched, thereby improving the light beam restriction capability of the InGaN straight waveguide. For the photodetector part, the p-GaN layer of the detector part is etched, and the InGaN / GaN quantum well diode device can realize the dual functions of LED and detector. Through the InGaN straight waveguide, two diode devices serving as Micro-LED and detector are integrated, an in-plane high-speed full-duplex visible light communication (VLC) system is realized, the problem of low modulation bandwidth of the existing visible light communication system is solved, and the performance of the visible light communication system can be improved.

[0071] The embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other.

[0072] The principles and implementation modes of the present application are described by using specific examples in this paper, and the above description of the embodiments is only used to help understand the system and core idea of the present application; at the same time, for those skilled in the art, according to the idea of the present application, the specific implementation mode and application range will be changed. In view of the above, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A full-duplex visible light communication system, characterized in that, include: ontology; The main body is divided into a transmitting area, a straight waveguide area, and a photoelectric detection area from left to right; A first AlGaN barrier layer is grown on top of the body within the emission region; a first two-dimensional electron gas layer is generated at the interface between the body within the emission region and the first AlGaN barrier layer; a first p-type GaN layer, a source, and a gate are grown on the first AlGaN barrier layer; a thin film layer is grown on the first p-type GaN layer; and a drain is grown on the thin film layer. A second AlGaN barrier layer is grown on the top of the body within the photodetector region; a second two-dimensional electron gas layer is generated at the interface between the body and the second AlGaN barrier layer within the photodetector region; a second p-type GaN layer and a cathode are grown on the second AlGaN barrier layer; an anode is grown on the second p-type GaN layer. The body, the first AlGaN barrier layer, and the first two-dimensional electron gas layer within the emission region constitute a driving transistor; the source, the gate, and the drain serve as electrodes of the driving transistor; the first two-dimensional electron gas layer, the first AlGaN barrier layer, the first p-type GaN layer, and the thin film layer constitute a Micro-LED; the drain serves as the anode of the Micro-LED, and the first two-dimensional electron gas layer serves as the cathode of the Micro-LED; the driving transistor is used to drive the Micro-LED to emit light.

2. The full-duplex visible light communication system according to claim 1, characterized in that, The body comprises: a substrate and a buffer layer, an intrinsic GaN layer, and an InGaN quantum well layer grown sequentially from bottom to top on the substrate.

3. A full-duplex visible light communication system according to claim 1, characterized in that, The thin film layer is a thin Ni / Au layer.

4. A full-duplex visible light communication system according to claim 2, characterized in that, The substrate is a silicon substrate.

5. A full-duplex visible light communication system according to claim 2, characterized in that, The substrate is a sapphire substrate, a silicon carbide substrate, or a gallium nitride substrate.

6. A full-duplex visible light communication system according to claim 2, characterized in that, The buffer layer is a gallium nitride layer doped with iron or carbon.

7. A full-duplex visible light communication system according to claim 2, characterized in that, The buffer layer is an AlGaN / GaN superlattice structure.

8. A method for fabricating a full-duplex visible light communication system, characterized in that, include: The main body is divided into the emission area, the straight waveguide area, and the photoelectric detection area from left to right; An AlGaN barrier layer and a p-type GaN layer are sequentially grown on the body from bottom to top; The AlGaN barrier layer and p-type GaN layer in the straight waveguide region are etched to achieve mesa isolation. A first AlGaN barrier layer is formed in the emitter region, and a second AlGaN barrier layer is formed in the photodetector region. A portion of the p-type GaN layer on the first AlGaN barrier layer is etched to obtain a first p-type GaN layer, and a portion of the p-type GaN layer on the second AlGaN barrier layer is etched to obtain a second p-type GaN layer. An ohmic contact metal is evaporated on the first AlGaN barrier layer, the second p-type GaN layer, and the second AlGaN barrier layer to obtain the source in the emitter region, the anode in the photodetector region, and the cathode in the photodetector region. A thin film layer is deposited on the first p-type GaN layer; A Schottky contact metal is evaporated on the first AlGaN barrier layer and the thin film layer to obtain the gate and drain in the emitter region.

9. A full-duplex visible light communication system according to claim 8, characterized in that, An ohmic contact metal is evaporated on the first AlGaN barrier layer, the second p-type GaN layer, and the second AlGaN barrier layer to obtain the source in the emitter region, the anode in the photodetector region, and the cathode in the photodetector region, specifically including: The surface of the device after the mesa isolation is completed is acid-treated to obtain the treated device; An ohmic contact metal is evaporated on the first AlGaN barrier layer, the second p-type GaN layer, and the second AlGaN barrier layer in the processed device using an electronic evaporation process, and then annealed at a set temperature to form the source in the emitter region, the anode in the photodetector region, and the cathode in the photodetector region.

10. A full-duplex visible light communication system according to claim 8, characterized in that, Depositing a thin film layer on the first p-type GaN layer specifically includes: A thin Ni / Au layer is deposited on top of the first p-type GaN layer using an electron beam evaporation process to form a thin film layer. The thin film layer is then annealed at a set temperature to form an ohmic contact between the thin film layer and the first p-type GaN layer.

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