HEMT-driven near-ultraviolet bidirectional optical communication monolithic integrated chip with wavelength of 365 nm and preparation method of HEMT-driven near-ultraviolet bidirectional optical communication monolithic integrated chip

Abstract

The invention belongs to the technical field of optical communication chips, and particularly relates to an HEMT (High Electron Mobility Transistor)-driven near ultraviolet bidirectional optical communication monolithic integrated chip with the wavelength of 365 nm and a preparation method thereof. Functions of an optical transmitter, an optical receiver and a driver are integrated into one chip, light emitted by a transmitting end is coupled into an optical waveguide and is detected by a photoelectric detector, an optical signal is converted into an electric signal, information transmission in the chip is completed, and a bidirectional optical communication link can be constructed without two sets of optical transmitters and optical receivers; the DBR Bragg reflection layer is adopted to reflect emergent light in all directions back to the waveguide of the straight waveguide area, so that the emergent light is transmitted to a receiving end along the waveguide of the straight waveguide area, by designing the material and period of the DBR, about 70% of the emergent light can be reflected, and the detection accuracy is improved; the integrated HEMT drive reduces the size and complexity of the whole circuit, the HEMT can still keep good linear performance under high current, distortion is reduced, and the stability of LED light output is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical communication chips, and in particular relates to a near-ultraviolet bidirectional optical communication monolithic integrated chip with a wavelength of 365nm driven by a HEMT and a preparation method thereof. Background Art

[0002] Visible light communication (VLC) uses the high-speed brightness changes of LED lights to quickly transmit data. It has huge spectrum potential and can meet the needs of higher capacity and ultra-high experience rate. The monolithic optoelectronic integrated chip integrates the optical transmitter, optical receiver and driving functions into one chip, overcoming the shortcomings of the traditional two-way optical communication link that requires two sets of optical transmitters and optical receivers to achieve two-way optical signal transmission. It also uses GaN-based HEMTs with high electron mobility, high withstand voltage and low on-resistance to drive LEDs, which can greatly reduce the complexity of the modulation circuit and realize voltage-controlled modulation of the light source.

[0003] LEDs used as communication light sources are current-driven devices, and AC signals cannot directly drive LEDs, so most current VLC systems use Bias-Tee biasers to drive LEDs. However, separate drive circuits have large parasitic capacitance and inductance, which increases power and generates heat.

[0004] LEDs in the visible light band mainly emit TE polarized photons, which is not conducive to lateral light coupling and propagation along the waveguide. However, as the wavelength decreases, ultraviolet light gradually transforms from TE to TM mode, which is more conducive to transmission along the waveguide.

[0005] In addition, there are currently two types of HEMT-LED monolithic integration process technologies at the chip level. One is to grow a HEMT (LED) structure on an LED (HEMT) structure through secondary epitaxy technology; the other is to connect the electrodes of the HEMT device to the electrodes of the LED through metal connections. The first method is prone to defects and etching damage, resulting in reduced luminous efficiency and increased on-resistance, while the second method introduces metal resistance, generating additional parasitic resistance.

[0006] In summary, it is necessary to develop a bidirectional optical communication integrated chip with simple preparation process, excellent conductive performance, concentrated optical path and enhanced modulation bandwidth. Summary of the invention

[0007] In view of the above problems, the object of the present invention is to provide a 365nm wavelength near-ultraviolet bidirectional optical communication monolithic integrated chip driven by a HEMT and a preparation method thereof.

[0008] The technical contents of the present invention are as follows: The present invention provides a near-ultraviolet bidirectional optical communication monolithic integrated chip with a wavelength of 365nm driven by a HEMT. The chip comprises a transmitting end composed of a HEMT-LED, a straight waveguide region and a receiving end composed of a photodetector. The transmitting end and the receiving end are connected through the straight waveguide region.

[0009] The emitter comprises a first AlGaN / GaN quantum well layer, a first DBR Bragg reflection layer, a first ITO current spreading layer, a source electrode, a gate electrode, a drain electrode, a passivation layer and a sidewall reflection layer; The structure thereof comprises, from bottom to top, a first AlGaN / GaN quantum well layer, a first DBR Bragg reflection layer, and a source electrode, a passivation layer, a gate electrode, a passivation layer, a first ITO current spreading layer and a drain electrode which are sequentially distributed laterally on the first DBR Bragg reflection layer, wherein the drain electrode is located on the first ITO current spreading layer, and also includes a side wall reflection layer grown on the side wall of the emitter; The last layer of the first AlGaN / GaN quantum well layer close to the first DBR Bragg reflection layer is a GaN layer, and the two-dimensional electron gas (2DEG) formed between the first DBR Bragg reflection layer and the GaN layer, and the two-dimensional electron gas (2DEG) formed at the interface of the AlGaN layer with different Al components in the first DBR Bragg reflection layer, together provide the electrons required for luminescence, and the three periods of the upper DBR close to the ITO current extension layer are p-type doped to provide the holes required for luminescence, and together constitute the LED region, and the gate structure controls the luminescence and luminous intensity of the LED by adjusting the gate voltage, forming the emission end driven by the HEMT to emit a light signal. The first DBR Bragg reflection layer is formed by alternating deposition of several periods of high refractive index material layers and low refractive index material layers, and the single layer thickness d satisfies d=λ / 4N (N is the refractive index of the layer, λ is the reflection wavelength), which is used to reflect the light incident on it to further concentrate the light path. The DBR Bragg reflection layer is composed of two AlGaN layers with different Al components with a period of p=5, with Al components of 0.18 and 0.65 respectively, with a total of 2p+1 layers. The three periods above are Mg-doped, with a doping concentration of 1×10 17 ~2×10 18 cm -3 , as the p-type layer of the emitter; wherein the last layer close to the first ITO current spreading layer is a 0.18 AlGaN layer, which also serves as the current blocking layer of the emitter; in the period below the p-type layer, no p-type doping is performed; the last layer close to the first AlGaN / GaN quantum well layer is a 0.18 AlGaN layer, which also serves as the barrier layer of the emitter; The source electrode is prepared on the first DBR Bragg reflection layer; The gate electrode is inserted into the first AlGaN / GaN quantum well layer through the first DBR Bragg reflection layer, and partially covers the surface of the first DBR Bragg reflection layer. The insertion layer is used to fully regulate the 2DEG formed between the AlGaN layers with different Al components in the DBR; The drain electrode is prepared on the first ITO current spreading layer; The passivation layer is filled in the gaps between the source metal layer and the gate metal layer and between the gate metal layer and the drain metal layer, and is made of SiO 2 、Si 3 N 4 Insulating materials such as , used to isolate the electrical connection between the source, gate and drain electrodes; The side wall reflection layer is coated on the side wall without waveguide connection at the emitting end and the bottom of the substrate to reflect the light emitted in other directions so that more light enters the waveguide area. It uses metal reflection films such as Al mirrors and Ag mirrors that can reflect visible light.

[0010] The receiving end comprises a second AlGaN / GaN quantum well layer, a second DBR Bragg reflection layer, a second ITO current spreading layer, a p-electrode layer, and an n-electrode layer; The structure thereof from bottom to top comprises a second AlGaN / GaN quantum well layer, a second DBR Bragg reflection layer, a second ITO current spreading layer, a p-electrode layer, and an n-electrode layer grown on the n-type platform of the second AlGaN / GaN quantum well layer; Among them, the epitaxial structures of the second AlGaN / GaN quantum well layer, the second DBR Bragg reflection layer, and the second ITO current spreading layer have the same functions as the first AlGaN / GaN quantum well layer, the first DBR Bragg reflection layer, and the first ITO current spreading layer at the emission end; The p-electrode layer is prepared on the second ITO current spreading layer; The n-electrode layer is prepared on an n-type platform, and the n-type platform is formed by etching the receiving end epitaxial stack to the second AlGaN / GaN quantum well layer; The substrate is one of sapphire, Si, SiC, GaN or quartz glass substrate, and the buffer layer is AlN; The straight waveguide region is composed of an AlGaN layer, a buffer, a substrate and a bottom reflection layer, and is used to connect the transmitting end and the receiving end, and couple the optical signal emitted by the transmitting end to the receiving end.

[0011] The thickness of the AlGaN layer is 1.5 μm, the period of the first and second AlGaN / GaN quantum well layers is 1 to 10, and in a single period, the thickness a1 of the single-layer AlGaN quantum barrier is 6 to 15 nm; the thickness a2 of the single-layer quantum well is 2 to 5 nm; the period p of the DBR Bragg reflection layer is 5, and in a single period, the thickness of the AlGaN with an Al component of 0.18 is 37 nm, the thickness of the AlGaN with an Al component of 0.65 is 40 nm, and the thickness of the ITO current spreading layer is 40 nm.

[0012] The present invention also provides a method for preparing a near-ultraviolet bidirectional optical communication monolithic integrated chip with a wavelength of 365nm driven by a HEMT, comprising the following steps: A buffer layer, an AlGaN waveguide layer, an AlGaN / GaN quantum well layer, a DBR Bragg reflection layer, and an ITO current spreading layer are sequentially grown on a substrate to obtain an epitaxial wafer; the middle of the epitaxial wafer is etched from top to bottom along a direction perpendicular to the substrate to the AlGaN waveguide layer to form a transmitting end, a receiving end, and a straight waveguide region connecting the two ends; On the emitter stack, etching is performed from top to bottom in a direction perpendicular to the substrate to the first DBR Bragg reflection layer to form a first ITO current spreading layer; On the emitter stack, etching is performed from top to bottom along a direction perpendicular to the substrate to the first AlGaN / GaN quantum well layer to form a plurality of cavities, the gate metal insertion layer is filled in the cavities, and a part of the structure is placed on the surface of the first AlGaN barrier layer, parallel to the first ITO current spreading layer; On the receiving end stack, etching is performed from top to bottom along a direction perpendicular to the substrate to the second AlGaN / GaN quantum well layer to form a p-type layer and an n-type platform, and a p-electrode layer and an n-electrode layer are respectively provided; The ohmic contact metal is evaporated and deposited on the first ITO current spreading layer, the first DBR Bragg reflection layer, the second ITO current spreading layer and the second AlGaN / GaN quantum well layer respectively, and the source and drain of the emission end and the anode and cathode of the receiving end are formed correspondingly after annealing; and the Schottky contact metal is then evaporated and deposited in the etching cavity by electron beam to form a gate in the emission area; Forming a passivation layer, wherein the passivation layer is filled in the gaps between the source metal layer and the gate metal layer and between the gate metal layer and the drain metal layer; A reflective layer is coated on the side wall without waveguide connection at the emitting end and on the bottom of the substrate to reflect the light emitted in other directions and realize optical path concentration.

[0013] The beneficial effects of the present invention are as follows: The HEMT-driven 365nm wavelength near-ultraviolet bidirectional optical communication monolithic integrated chip of the present invention forms device isolation by etching on the same epitaxial wafer, etches the epitaxial wafer to the waveguide layer, and forms an LED transmitting end driven by the HEMT and a receiving end composed of a photodetector with the same epitaxial structure at the left and right ends respectively. The straight waveguide area is conducive to the transmission of the outgoing light to the receiving end for detection. In addition, the DBR Bragg reflection layer can reflect the outgoing light in all directions back to the straight waveguide area, so that it is transmitted to the receiving end along the straight waveguide area. By designing the material and period of the DBR, the reflection of about 70% of the outgoing light can be increased to improve the accuracy of detection; and the two-dimensional electron gas generated by the gate of the HEMT is regulated to control the current between the source and the drain to drive the LED. The two-dimensional electron gas in the HEMT and the holes formed by the p-type layer in the DBR together constitute the LED light-emitting area; the integrated HEMT drive reduces the volume and complexity of the overall circuit compared to the external bias device, and the HEMT can still maintain good linear performance at high current, reduce distortion, and ensure the stability of the LED light output.

[0014] The preparation method of the HEMT-driven near-ultraviolet bidirectional optical communication monolithic integrated chip with a wavelength of 365nm of the present invention integrates the functions of an optical transmitter, an optical receiver and a driver into one chip, and the light emitted by the transmitting end is coupled into the optical waveguide and detected by the photodetector, and the optical signal is converted into an electrical signal to complete the information transmission in the chip, and a bidirectional optical communication link can be constructed without two sets of optical transmitters and optical receivers; the transmitting end is a HEMT-LED structure, and the two-dimensional electron gas (2DEG) formed between the first DBR and the GaN layer below it, and the two-dimensional electron gas (2DEG) formed at the interface of the AlGaN layer with different Al components in the first DBR, together provide the electrons required for luminescence, and the three periods near the ITO layer in the DBR provide the holes required for luminescence, and the electrons and holes can be driven to recombine by adjusting the gate voltage of the HEMT to emit light signals; the first AlGaN / GaN quantum well layer The setting not only provides the electrons required for luminescence, but also improves the conduction current of HEMT; the DBR layer not only provides holes, but also reflects the light path into the waveguide, and can also serve as a barrier layer and an electron blocking layer; the gate electrode of the gate structure is an embedded type, realizing an enhanced device, the gate is inserted into the first AlGaN / GaN quantum well layer, and covers the surface of the first AlGaN barrier layer, and is inserted into the quantum well layer, so that the 2DEG formed between the AlGaN layers of different Al components in the DBR is fully regulated; the side wall reflection layer, the reflection layer at the bottom of the substrate and the DBR layer are used to realize the effective concentration of the light path, so that the optical signal is more coupled into the waveguide area; the chip process is simple, and the integration of LED and HEMT does not require secondary epitaxy or the introduction of new metal resistors, and the voltage-controlled device effectively simplifies the complexity of the modulation circuit of the traditional VLC system, thereby greatly reducing the parasitic resistance and improving the luminous efficiency and modulation bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the cross-sectional structure of the monolithic integrated chip of the present invention; Figure 2 This is a schematic diagram of the light emission from the transmitting end of the present invention; Figure 3 It is an equivalent schematic diagram of the transmitting end of the present invention; Figure 4 It is a schematic top view of the coated side wall reflective layer of the present invention; Figure 5 The figure is a flow chart of the chip preparation process of the present invention. DETAILED DESCRIPTION

[0016] The present invention is further described in detail below through specific implementation cases and accompanying drawings. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of protection of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art are all within the scope of the claims attached to this application.

[0017] Unless otherwise specified, all raw materials and reagents of the present invention are raw materials and reagents from the conventional market.

[0018] Example 1 A 365nm wavelength near-ultraviolet bidirectional optical communication monolithic integrated chip driven by HEMT The schematic diagram of its cross-section structure is as follows Figure 1 As shown, the chip comprises a bottom reflection layer 1, a substrate 2, a buffer layer 3, an AlGaN waveguide layer 4, and a transmitting end composed of a first AlGaN / GaN quantum well layer 501, a first DBR Bragg reflection layer 502, a first ITO current diffusion layer 503, a drain electrode 504, a gate electrode 505, a source electrode 506, a passivation layer 507 and a sidewall reflection layer 508, and a receiving end composed of a second AlGaN / GaN quantum well layer 601, a second DBR Bragg reflection layer 602, a second ITO current spreading layer 603, a p-electrode layer 604, and an n-electrode layer 605; The reflective layer 1 is a metal reflective film Ag mirror; The substrate 2 is preferably a sapphire substrate; The buffer layer 3 is made of AlN and has a thickness of 2.5 μm and is disposed on the substrate 2; The AlGaN waveguide layer 4 has a thickness of 1.5 μm and is disposed on the buffer layer 3; The period of the first AlGaN / GaN quantum well layer 501 and the second AlGaN / GaN quantum well layer 601 is selected to be 5. In a single period, the thickness a1 of a single-layer AlGaN quantum barrier is 9 nm; the thickness a2 of a single-layer quantum well is 3 nm. The thickness of the first DBR Bragg reflection layer 502 and the second DBR Bragg reflection layer 602 is 422 nm, and the two stacked materials are respectively AlGaN layers with Al components of 0.18 and 0.65, and the thicknesses are respectively 37 nm and 40 nm; the thickness of the first current spreading layer 503 and the second current spreading layer 603 is 40 nm, and indium tin oxide (ITO) is selected; The last layer of the first AlGaN / GaN quantum well layer 501 close to the first DBR Bragg reflection layer 502 is a GaN layer. The two-dimensional electron gas (2DEG) formed between the GaN layer and the DBR Bragg reflection layer 502, and the two-dimensional electron gas (2DEG) formed at the interface of the AlGaN layer with different Al components in the first DBR Bragg reflection layer 501, together provide the electrons required for luminescence, and the three periods of the upper DBR close to the ITO current spreading layer provide the holes (2DHG) required for luminescence, such as Figure 2 As shown, the two together constitute the LED region, and electrons and holes recombine under the action of an applied voltage to achieve light emission; The source electrode 506 is prepared on the first DBR Bragg reflection layer 502, the drain electrode 504 is prepared on the first current spreading layer 503, and the gate electrode 505 is inserted into the first AlGaN / GaN quantum well layer 501, with an insertion depth of 450nm, and partially covers the surface of the first DBR Bragg reflection layer 502, with a coverage thickness of 35nm. The 2DEG under the gate has a depletion effect, realizing an enhanced device, and the inserted gate 505 is used to fully regulate the 2DEG formed at the interface between the quantum well and the barrier in the first AlGaN / GaN quantum well layer 501 and at the interface of the AlGaN layer with different Al components in the first DBR Bragg reflection layer 501. The light emission and light emission intensity of the LED are controlled by regulating the gate voltage, forming the transmitting end of the LED driven by the HEMT to emit a light signal, and its equivalent schematic diagram is as follows Figure 3 As shown, the LED is changed from current drive to voltage drive, eliminating the need for an external bias device. Instead, the voltage is directly provided by the GaN-based hemt, which greatly simplifies the complexity of the modulation circuit of the traditional VLC system, thereby reducing the external parasitic resistance and capacitance, improving the modulation bandwidth, and using the HEMT with high electron mobility and high withstand voltage to drive the LED to emit light, which can also further improve the luminous intensity; in addition, the DBR Bragg reflection layer can reflect about 70% of the emitted light back to the waveguide, so that more light is transmitted along the waveguide to the detector, improving the accuracy; The passivation layer 507 is filled in the gaps between the source electrode 506 and the gate electrode 505 and between the gate electrode 505 and the drain electrode 504, and is preferably made of insulating material to isolate the electrical connection between the source, gate and drain electrodes; The side wall reflection layer 508 is coated on the side wall of the emitting end where there is no waveguide connection. The top view of the coating is as shown in FIG. Figure 4 As shown, it is used to reflect the light emitted toward the side wall so that more light is coupled into the waveguide, and a metal reflective film Ag mirror is preferably used; The receiving end p-electrode 604 is prepared on the second ITO current spreading layer 603, and is made of Ni / Au composite metal material; The n-electrode layer 605 is prepared on an n-type platform, which is formed by etching the receiving end epitaxial stack to the second AlGaN / GaN quantum well layer 601, with an etching depth of 450nm. The n-electrode layer is made of Ti / Al / Ni / Ag composite metal material; Due to the existence of Stokes shift, the emission spectrum and response spectrum of the AlGaN / GaN active region overlap, so it has the dual functions of emitting photons and detecting photons under different bias voltages. The second AlGaN / GaN quantum well layer 601 in the receiving end is used to absorb the light emitted by the transmitting end and transmitted by waveguide coupling to convert it into an electrical signal, thereby realizing information transmission within the chip.

[0019] Example 2 A method for preparing a 365nm wavelength near-ultraviolet bidirectional optical communication monolithic integrated chip driven by HEMT The preparation process diagram is as follows Figure 5 As shown, an AlN buffer layer 3, an AlGaN waveguide layer 4, an AlGaN / GaN quantum well layer, a DBR Bragg reflection layer, and an ITO current spreading layer are sequentially grown on a sapphire substrate 2 by using a MOCVD process to obtain an epitaxial wafer; Using an inductively coupled plasma etching (ICP) process, the middle of the epitaxial wafer is etched from top to bottom along a direction perpendicular to the substrate 2 to the AlGaN waveguide layer 4 to form a transmitting end, a receiving end and a straight waveguide region in the middle; On the emitter stack, ICP etching is used to etch from top to bottom along a direction perpendicular to the substrate 2 to the DBR Bragg reflection layer 502 to form a first current spreading layer 503; On the transmitting end stack, ICP etching is used to etch 450nm in a direction perpendicular to the substrate 2 to the first AlGaN / GaN quantum well layer 501 to form a plurality of cavities, so that the gate metal insertion layer is filled in the cavities and covers the surface of the first AlGaN barrier layer; on the receiving end stack, ICP etching is used to etch 450nm from top to bottom in a direction perpendicular to the substrate 2 to the second AlGaN / GaN quantum well layer 601 to form the second ITO current spreading layer 603, the second DBR Bragg reflection layer 602, the second AlGaN / GaN quantum well layer 601 and the n-type platform, and the p-electrode and n-electrode described in Example 1 are prepared; By using an electron beam evaporation process, ohmic contact metal Ti / Al / Ni / Ag, Ti / Al / Ni / Ag, Ni / Au and Ti / Al / Ni / Ag composite metal materials are sequentially evaporated and deposited on the first DBR Bragg reflection layer 502, the first ITO current spreading layer 503, the second ITO current spreading layer 603 and the n-type layer, and rapidly annealed at 850° C. in a nitrogen atmosphere to form a source and a drain at the emission end, and an anode and a cathode at the receiving end; then, a Schottky contact metal Ni / Au composite metal electrode is evaporated and deposited in the cavity of the first AlGaN / GaN quantum well 501, and annealed in a nitrogen atmosphere at 40° C. to form a gate 507 in the emission region; Using an ion enhanced chemical vapor deposition (PECVD) process, a passivation layer 508 is deposited in the gaps between the source electrode 506 and the gate electrode 505 and between the gate electrode 505 and the drain electrode 504 to isolate the electrical connection between the source, gate and drain electrodes; A side wall reflection layer 508 and a reflection layer 1 are coated on the side wall without waveguide connection at the emission end and the bottom of the substrate to reflect the light emitted in other directions and realize optical path concentration.

[0020] The preparation process provided by Example 2 of the present invention is simple, wherein the integration process of the LED and HEMT in the emission end does not require secondary epitaxy or the introduction of new metal resistors, thereby effectively reducing the harm of reduced luminous efficiency caused by etching damage and defects, while reducing the internal parasitic resistance and improving the modulation bandwidth.

[0021] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A 365nm wavelength near-ultraviolet bidirectional optical communication monolithic integrated chip driven by HEMT, characterized in that: The chip comprises three parts: a transmitting end composed of a HEMT-LED, a straight waveguide area and a receiving end composed of a photodetector. The transmitting end and the receiving end are connected through the straight waveguide area.

2. The near-ultraviolet bidirectional optical communication monolithic integrated chip according to claim 1, characterized in that: The emitter comprises a first AlGaN / GaN quantum well layer, a first DBR Bragg reflection layer, a first ITO current spreading layer, a source electrode, a gate electrode, a drain electrode, a passivation layer and a sidewall reflection layer; Its structure from bottom to top includes a first AlGaN / GaN quantum well layer, a first DBR Bragg reflection layer, and a source electrode, a passivation layer, a gate electrode, a passivation layer, a first ITO current spreading layer and a drain electrode which are laterally distributed in the first DBR Bragg reflection layer in sequence, wherein the drain electrode is located on the first ITO current spreading layer, and also includes a side wall reflection layer grown on the side wall of the emitter.

3. The near-ultraviolet bidirectional optical communication monolithic integrated chip according to claim 2, characterized in that: The last layer of the first AlGaN / GaN quantum well layer close to the first DBR Bragg reflection layer is a GaN layer. The two-dimensional electron gas (2DEG) formed between the first DBR Bragg reflection layer and the GaN layer, and the two-dimensional electron gas (2DEG) formed at the interface of AlGaN layers with different Al components in the first DBR Bragg reflection layer together constitute the LED area. The gate structure controls the light emission and light emission intensity of the LED by adjusting the gate voltage, forming the emission end at which the HEMT drives the LED to emit a light signal.

4. The near-ultraviolet bidirectional optical communication monolithic integrated chip according to claim 2, characterized in that: The first DBR Bragg reflection layer is formed by alternately depositing a plurality of periods of high refractive index material layers and low refractive index material layers, and the thickness d of a single layer satisfies d=λ / 4N, where N is the refractive index of the layer and λ is the reflection wavelength; The DBR Bragg reflection layer is composed of two AlGaN layers with different Al components in a period of p=5, with Al components of 0.18 and 0.65 respectively, with a total of 2p+1 layers. The upper three periods are Mg-doped with a doping concentration of 1×10 17 ~2×10 18 cm -3 , serving as the p-type layer of the emitter; the last layer close to the first ITO current spreading layer is a 0.18 AlGaN layer, which also serves as the current blocking layer of the emitter; in the period below the p-type layer, no p-type doping is performed; the last layer close to the first AlGaN / GaN quantum well layer is a 0.18 AlGaN layer, which also serves as the barrier layer of the emitter.

5. The near-ultraviolet bidirectional optical communication monolithic integrated chip according to claim 2, characterized in that: The source electrode is prepared on the first DBR Bragg reflection layer; The gate electrode is inserted into the first AlGaN / GaN quantum well layer through the first DBR Bragg reflection layer, and partially covers the surface of the first DBR Bragg reflection layer. The insertion layer is used to fully regulate the 2DEG formed between the AlGaN layers with different Al components in the DBR; The drain electrode is prepared on the first ITO current spreading layer; The passivation layer is filled in the gaps between the source metal layer and the gate metal layer and between the gate metal layer and the drain metal layer, and is made of insulating material.

6. The near-ultraviolet bidirectional optical communication monolithic integrated chip according to claim 2, characterized in that: The side wall reflection layer is coated on the side wall of the emitting end without waveguide connection and the bottom of the substrate, and a metal reflection film capable of reflecting visible light is selected.

7. The near-ultraviolet bidirectional optical communication monolithic integrated chip according to claim 1, characterized in that: The receiving end comprises a second AlGaN / GaN quantum well layer, a second DBR Bragg reflection layer, a second ITO current spreading layer, a p-electrode layer, and an n-electrode layer; The structure thereof from bottom to top comprises a second AlGaN / GaN quantum well layer, a second DBR Bragg reflection layer, a second ITO current spreading layer, a p-electrode layer and an n-electrode layer grown on an n-type platform of the second AlGaN / GaN quantum well layer.

8. The near-ultraviolet bidirectional optical communication monolithic integrated chip according to claim 7, characterized in that: The epitaxial structure of the second AlGaN / GaN quantum well layer, the second DBR Bragg reflection layer, and the second ITO current spreading layer and the first AlGaN / GaN quantum well layer, the first DBR Bragg reflection layer, and the first ITO current spreading layer function as the emission end; The p-electrode layer is prepared on the second ITO current spreading layer; The n-electrode layer is prepared on an n-type platform, and the n-type platform is formed by etching the receiving end epitaxial stack to the second AlGaN / GaN quantum well layer.

9. The near-ultraviolet bidirectional optical communication monolithic integrated chip according to claim 1, characterized in that: The straight waveguide region is composed of an AlGaN layer, a buffer, a substrate and a bottom reflective layer, connects the transmitting end and the receiving end, and couples the optical signal emitted by the transmitting end to the receiving end; The substrate includes a sapphire, Si, SiC, GaN or quartz glass substrate; the buffer layer includes AlN; The thickness of the AlGaN layer is 1.5 μm, the period of the first AlGaN / GaN quantum well layer at the transmitting end and the second AlGaN / GaN quantum well layer at the receiving end is 1-10, and in a single period, the thickness a1 of a single-layer AlGaN quantum barrier is 6-15 nm; the thickness a2 of a single-layer quantum well is 2-5 nm; The period p of the DBR Bragg reflection layer at the transmitting end and the receiving end is 5, and in a single period, the thickness of AlGaN with an Al component of 0.18 is 37 nm, and the thickness of AlGaN with an Al component of 0.65 is 40 nm; The thickness of the ITO current spreading layer at the transmitting end and the receiving end is 40nm.

10. A method for preparing a 365nm wavelength near-ultraviolet bidirectional optical communication monolithic integrated chip driven by a HEMT according to any one of claims 1 to 9, characterized in that: The steps include: A buffer layer, an AlGaN waveguide layer, an AlGaN / GaN quantum well layer, a DBR Bragg reflection layer, and an ITO current spreading layer are sequentially grown on a substrate to obtain an epitaxial wafer; Etching the middle of the epitaxial wafer from top to bottom in a direction perpendicular to the substrate to the AlGaN waveguide layer to form a transmitting end, a receiving end, and a straight waveguide region connecting the two ends; On the emitter stack, etching is performed from top to bottom in a direction perpendicular to the substrate to the first DBR Bragg reflection layer to form a first ITO current spreading layer; On the emitter stack, etching is performed from top to bottom along a direction perpendicular to the substrate to the first AlGaN / GaN quantum well layer to form a plurality of cavities, the gate metal insertion layer is filled in the cavities, and a part of the structure is placed on the surface of the first AlGaN barrier layer, parallel to the first ITO current spreading layer; On the receiving end stack, etching is performed from top to bottom along a direction perpendicular to the substrate to the second AlGaN / GaN quantum well layer to form a p-type layer and an n-type platform, and a p-electrode layer and an n-electrode layer are respectively provided; The ohmic contact metal is evaporated and deposited on the first ITO current spreading layer, the first DBR Bragg reflection layer, the second ITO current spreading layer and the second AlGaN / GaN quantum well layer respectively, and the source and drain of the transmitting end and the anode and cathode of the receiving end are formed correspondingly after annealing; Then, a Schottky contact metal is deposited in the etched cavity by electron beam evaporation to form a gate in the emitter region; Forming a passivation layer, wherein the passivation layer is filled in the gaps between the source metal layer and the gate metal layer and between the gate metal layer and the drain metal layer; A reflective layer is coated on the side wall without waveguide connection at the transmitting end and on the bottom of the substrate, so as to prepare a bidirectional optical communication monolithic integrated chip.

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