Gallium nitride LED and germanium PD monolithic heterogeneous integrated structure and preparation method thereof

Abstract

The invention relates to the technical field of semiconductor devices and manufacturing thereof, and discloses a gallium nitride LED and germanium PD monolithic heterogeneous integrated structure and a preparation method thereof.The gallium nitride LED and the germanium PD are arranged side by side, and semiconductor materials of all layers are epitaxially grown on a silicon substrate layer; the gallium nitride LED device structurally comprises a buffer layer, an N-type gallium nitride layer, a multi-quantum well light-emitting layer and a P-type gallium nitride layer from bottom to top, metal electrodes are arranged on the N-type gallium nitride layer and the P-type gallium nitride layer, the germanium photoelectric detector sequentially comprises a silicon substrate, a P-type germanium layer, an intrinsic germanium layer and an N-type germanium layer from bottom to top, metal electrodes are arranged on the P-type germanium layer and the N-type germanium layer, and metal electrodes are arranged on the intrinsic germanium layer and the N-type germanium layer. The silicon-based gallium nitride LED and the germanium-based photoelectric detector are integrated on the same silicon substrate, so that the integration level of the whole system is enhanced, the size of the system is effectively reduced, and the functions of an existing single illumination system are enriched.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices and manufacturing thereof, and in particular to a gallium nitride LED and a germanium PD monolithic heterogeneous integrated structure and a preparation method thereof. Background Art

[0002] Gallium nitride (GaN) materials have shown significant advantages in LED manufacturing, including their wide spectrum coverage, which can cover the entire visible light region, part of the infrared and deep ultraviolet regions by adjusting the alloy component ratio. GaN is a direct bandgap semiconductor, which makes it excellent in electro-optical conversion efficiency. In addition, GaN-based LEDs have high brightness, high efficiency, good thermal performance, high radiation resistance, high frequency and high power characteristics, chemical stability, high hardness and high melting point. It has shown great potential in lighting, display technology, communication and other fields. These characteristics of GaN materials have enabled it to occupy an important position in LED technology and promoted the development and innovation of lighting technology.

[0003] More and more practical applications require higher integration, smaller size, lighter weight, and more functional lighting systems. It is necessary to integrate chips with various functions such as lighting, photosensitivity, power management, driving, digital processing, etc. in the smallest possible area.

[0004] However, the GaN LED lighting systems currently on the market often only have a single light-emitting function and are unable to adjust the switch and brightness conversion of the lighting system in time according to the real-time changes in the application scenario, resulting in a large amount of electric energy waste and greatly shortening the service life of the lighting system. Even the light-emitting system with the addition of photosensitive elements still has defects such as slow signal response speed, low integration, and complex packaging. Therefore, it is necessary to integrate components that sense changes in ambient light on a monolithic chip on the LED in the lighting system.

[0005] To this end, we propose a monolithic heterogeneous integrated structure of gallium nitride LED and germanium PD and its preparation method. Compared with silicon photodetectors, germanium photodetectors (PDs) have higher absorption coefficients and direct band gaps in the near-infrared band, which makes them perform better in light absorption efficiency and response speed. The high electron and high hole mobility of germanium helps to achieve fast response, while its compatibility with CMOS process reduces manufacturing costs and improves device reliability. In addition, the high-frequency working capability and wavelength tuning capability of germanium PDs make them have broad application potential in fields such as high-speed optical communications and infrared imaging. Therefore, germanium PDs provide significant advantages over silicon photodetectors in terms of performance and cost-effectiveness. Summary of the invention

[0006] In order to make up for the shortcomings of the prior art, the present invention provides the following technical solutions: a gallium nitride LED and germanium PD monolithic heterogeneous integrated structure and a preparation method thereof, comprising a silicon substrate layer, the bottom layer being the silicon substrate layer, the gallium nitride LED and the germanium PD being arranged side by side on the same silicon substrate layer, the various layers of semiconductor materials of the gallium nitride LED and the germanium PD being epitaxially grown on the silicon substrate layer, the gallium nitride LED being used as a light-emitting device to emit light, and the germanium PD being used as a light-detecting device to detect external incident light, or to detect light emitted by the gallium nitride LED next to it.

[0007] Preferably, one side of the gallium nitride LED includes a buffer layer, an N-type gallium nitride layer, a multi-quantum well light-emitting layer, a P-type gallium nitride layer, a P-type gallium nitride layer metal electrode and an N-type gallium nitride layer metal electrode. When a forward voltage is applied to the metal electrode, the N-type gallium nitride layer injects electrons into the multi-quantum well light-emitting layer, and the P-type gallium nitride layer injects holes into the multi-quantum well light-emitting layer. The electrons and holes recombine in the multi-quantum well light-emitting layer to emit light.

[0008] Preferably, one side of the germanium-based PD is composed of an N-type germanium layer, a P-type germanium layer, a P-type germanium metal electrode and an N-type germanium metal electrode from bottom to top. A depletion region is formed between the N-type germanium layer and the P-type germanium layer, and the direction of its built-in potential field is from the N region to the P region. The electrode increases the level compared to the electrode to make the diode in a reverse biased state. When external light is incident, photogenerated carriers are generated, thereby forming a photogenerated current in the external circuit. The above metal electrodes all form ohmic contact with the semiconductor layer below.

[0009] Preferably, a germanium PIN photodetector intrinsic germanium layer is arranged between the N-type germanium layer and the P-type germanium layer, and a wider depletion region is formed between the N-type germanium layer and the P-type germanium layer, and the direction of its built-in potential field is from the N region to the P region. The electric field separates the photogenerated carriers, pushes the photogenerated electrons to the N region, and pushes the photogenerated holes to the P region. Under the action of the external circuit, the separation and movement of electrons and holes form a photocurrent, which is proportional to the intensity of the incident light and is monitored by the external circuit.

[0010] Preferably, the germanium photodetector has a structure of, from bottom to top, a P-type germanium layer, a P-type germanium metal contact and a P-type germanium metal contact, wherein the P-type germanium metal contact is a Schottky contact, and a Schottky barrier is formed between the metal layer and the P-type germanium. When light irradiates the P-type germanium layer, photogenerated carriers are generated, and the photogenerated carriers are converted into photocurrent under the combined action of an external electric field and the Schottky barrier. The current is proportional to the intensity of the incident light and is monitored by an external circuit, and an ohmic contact is formed between the P-type germanium metal contact and the P-type germanium layer.

[0011] Preferably, the buffer layer material of the gallium nitride LED is gallium nitride or aluminum gallium nitride, with a thickness of 200-2000nm, which can be grown by MOCVD (metal organic chemical vapor deposition) equipment or MBE (molecular beam epitaxy) equipment. The multi-quantum well light-emitting layer of the gallium nitride LED is composed of alternately stacked InGaN (indium gallium nitride) and GaN layers, wherein the indium gallium nitride layer is a quantum well, and the GaN layer is a quantum barrier. The multi-quantum well includes multiple periods of quantum wells and barriers, each period is called a pair of quantum well / barrier pairs, the quantum well thickness is 2-10nm, and the quantum barrier thickness is 10-20nm. The quantum wells and quantum barriers are grown by MOCVD or MBE, the quantum wells are grown at a lower temperature, and the quantum barriers are grown at a higher temperature.

[0012] The N-type gallium nitride layer of the gallium nitride LED is doped with group IV elements such as germanium and silicon while growing to achieve N-type doping, and the P-type gallium nitride layer is doped with magnesium while growing to achieve P-type doping. The metal electrodes of the P-type gallium nitride layer and the N-type gallium nitride layer of the gallium nitride LED are multi-layer structures, which are ITO (indium tin oxide) and other metals or Cr and other metals from bottom to top.

[0013] Preferably, the N-type germanium layer of the germanium photodetector is grown by MOCVD or MBE, and its doping can be achieved by doping with group V elements while growing or by ion implantation of group V elements after growth. The P-type germanium layer of the germanium photodetector is grown by MOCVD or MBE, and its doping can be achieved by doping with group V elements while growing or by ion implantation of group III elements after growth.

[0014] Preferably, the metal contact of the germanium photodetector is a multilayer structure of ITO / TaN / TiNx / WNx / a-Ge / GeONx / GeSnOx and other metals.

[0015] Preferably, the Schottky metal contact of the germanium photodetector is Al or NiGe.

[0016] Preferably, the method comprises the following steps:

[0017] Step 1: Select a silicon substrate layer and clean the pollutants on the surface of the silicon substrate layer;

[0018] Step 2: sequentially growing a buffer layer, an N-type gallium nitride layer, a multi-quantum well light-emitting layer, and a P-type gallium nitride layer;

[0019] Step 3: Grooving the structural part obtained in step 2, growing germanium epitaxial materials in sequence, and doping germanium during growth to obtain N-type germanium layer and P-type germanium layer of the germanium photodetector;

[0020] Step 4: preparing a P-type gallium nitride layer metal electrode and an N-type gallium nitride layer metal electrode;

[0021] Step 5: Prepare a metal electrode and an N-type germanium metal electrode on the germanium material obtained in step 4.

[0022] Beneficial Effects

[0023] Compared with the prior art, the present invention provides a gallium nitride LED and germanium PD monolithic heterogeneous integrated structure and a preparation method thereof, which has the following beneficial effects:

[0024] The present invention allows the integration of light emitting diodes (LEDs) and photodetectors (PDs) on the same chip. This increased integration reduces the need for external connections and packaging, making the system more compact, helping to reduce device failure points, thereby improving system stability and service life.

[0025] The integrated device of the present invention can not only realize the emission and detection of light, but also realize the routing of optical signals through waveguides, thereby expanding the functions of the system and enabling it to be applied to a wider range of fields, such as optical communication, optical interconnection, and visible light communication.

[0026] The integrated device of the present invention can generate electrical signals by sensing changes in external light, thereby realizing perception of the environment, thereby being able to intelligently regulate the brightness and switching of LEDs, greatly reducing the energy consumption of the system.

[0027] The germanium photodetector of the present invention is compatible with the silicon-based integrated circuit manufacturing process, which enables the manufacturing process of the integrated GaN LED and germanium photodetector to utilize the existing Si production line, thereby reducing the manufacturing cost and increasing the production efficiency.

[0028] The integrated LED and PD exhibit a fast response on the nanosecond time scale and can transmit data signals at very high rates, which is particularly important for high-speed optical communication and optical interconnect applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of Embodiment 1 of a gallium nitride LED and germanium PD monolithic heterogeneous integrated structure and a preparation method thereof of the present invention;

[0030] Figure 2 This is a schematic diagram of the structure of Embodiment 2 of a gallium nitride LED and a germanium PD monolithic heterogeneous integrated structure and a preparation method thereof of the present invention;

[0031] Figure 3 It is a structural schematic diagram of Embodiment 3 of a gallium nitride LED and germanium PD monolithic heterogeneous integrated structure and a preparation method thereof of the present invention;

[0032] Figure 4 It is a schematic diagram of a manufacturing method of a gallium nitride LED and a germanium PD monolithic heterogeneous integrated structure and a manufacturing method thereof of the present invention.

[0033] In the figure: 1. Silicon substrate layer; 2. Buffer layer; 3. N-type gallium nitride layer; 4. Multi-quantum well light-emitting layer; 5. P-type gallium nitride layer; 6. P-type gallium nitride layer metal electrode; 7. N-type gallium nitride layer metal electrode; 8. N-type germanium layer; 81. Intrinsic germanium layer of germanium PIN photodetector; 9. P-type germanium layer; 91. P-type germanium layer Schottky contact; 10. P-type germanium metal electrode; 101. P-type germanium ohmic contact; 11. N-type germanium metal electrode. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments 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.

[0035] Embodiment 1:

[0036] like Figure 1 As shown, it is a schematic diagram of a monolithic heterogeneous integrated structure of a gallium nitride LED and a germanium PD proposed in the present invention, wherein the structure comprises, from bottom to top, a silicon substrate layer 1, a buffer layer 2, an N-type gallium nitride layer 3, a multi-quantum well light-emitting layer 4, a P-type gallium nitride layer 5, a P-type gallium nitride layer metal electrode 6, an N-type gallium nitride layer metal electrode 7, an N-type germanium layer 8, a P-type germanium layer 9, a P-type germanium metal electrode 10 and an N-type germanium metal electrode 11.

[0037] The P-type gallium nitride layer metal electrode 6 and the N-type gallium nitride layer metal electrode 7 both form ohmic contacts with the underlying semiconductor layer.

[0038] The P-type germanium metal electrode 10 and the N-type germanium metal electrode 11 both form ohmic contacts with the underlying germanium semiconductor layer.

[0039] Specifically, the doping element of the P-type gallium nitride layer 5 is Mg, and the doping concentration is 1×10 18 cm -3 -1x10 21 cm -3 .

[0040] Preferably, the Mg doping concentration is 5x1019cm -3 .

[0041] The multi-quantum well light-emitting layer 4 is formed by sequentially overlapping an InGaN layer and a GaN layer.

[0042] Specifically, the buffer layer 2 is made of gallium nitride or AlGaN, with a thickness of 200-2000 nm.

[0043] Preferably, the buffer layer 2 is made of gallium nitride with a thickness of 300 nm.

[0044] Specifically, each layer of material on the epitaxial layer is grown using MOCVD or MBE.

[0045] Preferably, each layer of material on the epitaxial layer is grown using MOCVD.

[0046] Specifically, the growth temperature of the InGaN layer in the multi-quantum well light-emitting layer 4 is 550°C-700°C, and the growth temperature of the GaN layer is 700°C-900°C.

[0047] Preferably, the growth temperature of the InGaN layer in the multi-quantum well light-emitting layer 4 is 720°C, and the growth temperature of the GaN layer is 840°C.

[0048] Specifically, the doping element of the N-type gallium nitride layer 3 is germanium or silicon.

[0049] Preferably, the doping element of the N-type gallium nitride layer 3 is silicon.

[0050] Specifically, each metal electrode is a multi-layer structure, which includes ITO (indium tin oxide) and other metals or Cr and other metals from bottom to top.

[0051] Preferably, the metal electrodes are respectively ITO (indium tin oxide) and other metals from bottom to top.

[0052] Specifically, the doping elements of the N-type germanium layer 8 are P and Bi, and the doping elements of the P-type germanium layer 9 are B, Al or Ga.

[0053] Preferably, the doping element of the N-type germanium layer 8 is Bi, and the doping element of the P-type germanium layer 9 is B.

[0054] Embodiment 2:

[0055] like Figure 2 As shown, it is a schematic diagram of a monolithic heterogeneous integrated structure of a gallium nitride LED and a germanium PD proposed in the present invention, wherein the structure comprises, from bottom to top, a silicon substrate layer 1, a buffer layer 2, an N-type gallium nitride layer 3, a multi-quantum well light-emitting layer 4, a P-type gallium nitride layer 5, a P-type gallium nitride layer metal electrode 6, an N-type gallium nitride layer metal electrode 7, a germanium PIN photodetector intrinsic germanium layer 81, an N-type germanium layer 8, a P-type germanium layer 9, a P-type germanium metal electrode 10 and an N-type germanium metal electrode 11.

[0056] The P-type gallium nitride layer metal electrode 6 and the N-type gallium nitride layer metal electrode 7 both form ohmic contacts with the underlying semiconductor layer.

[0057] The P-type germanium metal electrode 10 and the N-type germanium metal electrode 11 both form ohmic contacts with the underlying germanium semiconductor layer.

[0058] A PN junction is formed between the N-type germanium layer 8 and the P-type germanium layer 9 , which is located in the intrinsic germanium layer 81 of the germanium PIN photodetector. The direction of the built-in electric field is from the N-type germanium layer 8 to the P-type germanium layer 9 .

[0059] Specifically, the doping element of the P-type gallium nitride layer 5 is Mg, and the doping concentration is 1×10 18 cm -3 -1x10 21 cm -3 .

[0060] Preferably, the Mg doping concentration is 5x10 19 cm -3 .

[0061] The multi-quantum well light-emitting layer 4 is formed by sequentially overlapping an InGaN layer and a GaN layer.

[0062] Specifically, the buffer layer 2 is made of gallium nitride or AlGaN, with a thickness of 200-2000 nm.

[0063] Preferably, the buffer layer 2 is made of gallium nitride with a thickness of 300 nm.

[0064] Specifically, each layer of material on the epitaxial layer is grown using MOCVD or MBE.

[0065] Preferably, each layer of material on the epitaxial layer is grown using MOCVD.

[0066] Specifically, the growth temperature of the InGaN layer in the multi-quantum well light-emitting layer 4 is 550°C-700°C, and the growth temperature of the GaN layer is 700°C-900°C.

[0067] Preferably, the growth temperature of the InGaN layer in the multi-quantum well light-emitting layer 4 is 720°C, and the growth temperature of the GaN layer is 840°C.

[0068] Specifically, the doping element of the N-type gallium nitride layer 3 is germanium or silicon.

[0069] Preferably, the doping element of the N-type gallium nitride layer 3 is silicon.

[0070] Specifically, each metal electrode is a multi-layer structure, which includes ITO (indium tin oxide) and other metals or Cr and other metals from bottom to top.

[0071] Preferably, the metal electrodes are respectively ITO (indium tin oxide) and other metals from bottom to top.

[0072] Specifically, the doping elements of the N-type germanium layer 8 are P and Bi, and the doping elements of the P-type germanium layer 9 are B, Al or Ga.

[0073] Preferably, the doping element of the N-type germanium layer 8 is Bi, and the doping element of the P-type germanium layer 9 is B.

[0074] Specifically, the intrinsic germanium layer is grown by MOCVD or MBE.

[0075] Preferably, the intrinsic germanium layer is grown by MOCVD.

[0076] Embodiment three:

[0077] like Figure 3 As shown, it is a schematic diagram of a monolithic heterogeneous integrated structure of a gallium nitride LED and a germanium PD proposed in the present invention, wherein the structure comprises, from bottom to top, a silicon substrate layer 1, a buffer layer 2, an N-type gallium nitride layer 3, a multi-quantum well light-emitting layer 4, a P-type gallium nitride layer 5, a P-type gallium nitride layer metal electrode 6, an N-type gallium nitride layer metal electrode 7, a P-type germanium layer 9, a P-type germanium layer Schottky contact 91 and a P-type germanium ohmic contact 101.

[0078] The P-type gallium nitride layer metal electrode 6 and the N-type gallium nitride layer metal electrode 7 both form ohmic contacts with the underlying semiconductor layer.

[0079] The P-type germanium metal electrode 10 forms a P-type germanium layer Schottky contact 91 with the underlying germanium semiconductor layer, and the P-type germanium metal electrode 10 forms an ohmic contact with the underlying germanium semiconductor layer.

[0080] 8. The N-type germanium layer 8 and the P-type germanium layer Schottky contact 91 form a Schottky barrier, and the direction of the built-in electric field is from the N-type germanium layer 8 to the P-type germanium layer 9.

[0081] Specifically, the doping element of the P-type gallium nitride layer 5 is Mg, and the doping concentration is 1×10 18 cm -3 -1x10 21 cm -3 .

[0082] Preferably, the Mg doping concentration is 5x10 19 cm -3 .

[0083] The multi-quantum well light-emitting layer 4 is formed by sequentially overlapping an InGaN layer and a GaN layer.

[0084] Specifically, the buffer layer 2 is made of gallium nitride or AlGaN, with a thickness of 200-2000 nm.

[0085] Preferably, the buffer layer 2 is made of gallium nitride with a thickness of 300 nm.

[0086] Specifically, each layer of material on the epitaxial layer is grown using MOCVD or MBE.

[0087] Preferably, each layer of material on the epitaxial layer is grown using MOCVD.

[0088] Specifically, the growth temperature of the InGaN layer in the multi-quantum well light-emitting layer 4 is 550°C-700°C, and the growth temperature of the GaN layer is 700°C-900°C.

[0089] Preferably, the growth temperature of the InGaN layer in the multi-quantum well light-emitting layer 4 is 720°C, and the growth temperature of the GaN layer is 840°C.

[0090] Specifically, the doping element of the N-type gallium nitride layer 3 is germanium or silicon.

[0091] Preferably, the doping element of the N-type gallium nitride layer 3 is silicon.

[0092] Specifically, each metal electrode is a multi-layer structure, which includes ITO (indium tin oxide) and other metals or Cr and other metals from bottom to top.

[0093] Preferably, the metal electrodes are respectively ITO (indium tin oxide) and other metals from bottom to top.

[0094] Specifically, the doping element of the P-type germanium layer 9 is B, Al or Ga.

[0095] Preferably, the doping element of the P-type germanium layer 9 is B.

[0096] Embodiment 4:

[0097] like Figure 4 FIG. 1 is a schematic diagram of a method for manufacturing a monolithic heterogeneous integrated structure of a gallium nitride LED and a germanium photodetector proposed by the present invention, and the specific steps are as follows:

[0098] Step 1: cleaning pollutants on the surface of the silicon substrate layer 1;

[0099] Step 2: sequentially growing a buffer layer 2, an N-type gallium nitride layer 3, a multi-quantum well light-emitting layer 4 and a P-type gallium nitride layer 5;

[0100] Step 3: preparing a P-type gallium nitride layer metal electrode 6 and an N-type gallium nitride layer metal electrode 7;

[0101] Step 4: Grooving in the structural part area obtained in step 3 to sequentially grow germanium epitaxial material, and doping germanium during growth to obtain N-type germanium layer 8 and P-type germanium layer 9 of the germanium photodetector;

[0102] Step 5: Prepare a metal electrode on the germanium material obtained in step 4.

[0103] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0104] 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.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A gallium nitride LED and germanium PD monolithic heterogeneous integrated structure, characterized in that: The invention comprises a silicon substrate layer (1), wherein the bottom layer is the silicon substrate layer (1), a gallium nitride LED and a germanium PD are arranged side by side on the same silicon substrate layer (1), each layer of semiconductor material of the gallium nitride LED and the germanium PD is epitaxially grown on the silicon substrate layer (1), the gallium nitride LED is used as a light emitting device to emit light, and the germanium PD is used as a light detecting device to detect external incident light, or detect light emitted by the gallium nitride LED next to it.

2. The gallium nitride LED and germanium PD monolithic heterogeneous integrated structure according to claim 1, characterized in that: One side of the gallium nitride LED comprises a buffer layer (2), an N-type gallium nitride layer (3), a multi-quantum well light-emitting layer (4), a P-type gallium nitride layer (5), a P-type gallium nitride layer metal electrode (6) and an N-type gallium nitride layer metal electrode (7). When a forward voltage is applied to the P-type gallium nitride layer metal electrode (6), the N-type gallium nitride layer (3) injects electrons into the multi-quantum well light-emitting layer (4), and the P-type gallium nitride layer (5) injects holes into the multi-quantum well light-emitting layer (4). The electrons and holes recombine in the multi-quantum well light-emitting layer (4) to emit light.

3. A gallium nitride LED and germanium PD monolithic heterogeneous integrated structure according to claim 1, characterized in that: One side of the germanium-based PD is composed of an N-type germanium layer (8), a P-type germanium layer (9), a P-type germanium metal electrode (10) and an N-type germanium metal electrode (11) from bottom to top. A depletion region is formed between the N-type germanium layer (8) and the P-type germanium layer (9). The direction of the built-in electric potential field is from the N region to the P region. The N-type germanium metal electrode (11) increases the level compared to the P-type germanium metal electrode (10) to put the diode in a reverse bias state. When external light is incident, photogenerated carriers are generated, thereby forming a photogenerated current in the external circuit. The above metal electrodes all form ohmic contact with the semiconductor layer below.

4. The gallium nitride LED and germanium PD monolithic heterogeneous integrated structure according to claim 3, characterized in that: A germanium PIN photodetector intrinsic germanium layer (81) is arranged between an N-type germanium layer (8) and a P-type germanium layer (9), and a relatively wide depletion region is formed between the N-type germanium layer (8) and the P-type germanium layer (9). The direction of the built-in electric potential field is directed from the N region to the P region. The electric field separates the photogenerated carriers, pushes the photogenerated electrons to the N region, and pushes the photogenerated holes to the P region. Under the action of an external circuit, the separation and movement of electrons and holes form a photocurrent, and the current is proportional to the intensity of the incident light and is monitored by the external circuit.

5. The gallium nitride LED and germanium PD monolithic heterogeneous integrated structure according to claim 1, characterized in that: The germanium photodetector has a structure from bottom to top of a P-type germanium layer (9), a P-type germanium layer Schottky contact (91) and a P-type germanium ohmic contact (101). The P-type germanium layer Schottky contact (91) is a Schottky contact. A Schottky barrier is formed between the metal layer and the P-type germanium layer (9). When light irradiates the P-type germanium layer (9), photogenerated carriers are generated. Under the combined action of an external electric field and the Schottky barrier, the photogenerated carriers are converted into photocurrents. The current is proportional to the intensity of the incident light and is monitored by an external circuit. An ohmic contact is formed between the P-type germanium ohmic contact (101) and the P-type germanium layer (9).

6. The gallium nitride LED and germanium PD monolithic heterogeneous integrated structure according to claim 2, characterized in that: The buffer layer (2) of the gallium nitride LED is made of gallium nitride or aluminum gallium nitride, with a thickness of 200-2000nm, and can be grown by MOCVD (metal organic chemical vapor deposition) equipment or MBE (molecular beam epitaxy) equipment. The multi-quantum well light-emitting layer (4) of the gallium nitride LED is composed of alternately stacked InGaN (indium gallium nitride) and GaN layers, wherein the InGaN layer is a quantum well and the GaN layer is a quantum barrier. The multi-quantum well contains multiple periods of quantum wells and barriers, each period is called a quantum well / barrier pair, the quantum well thickness is 2-10nm, and the quantum barrier thickness is 10-20nm. The quantum well and the quantum barrier are grown by MOCVD or MBE, the quantum well is grown at a lower temperature, and the quantum barrier is grown at a higher temperature. The N-type gallium nitride layer (3) of the gallium nitride LED is doped with group IV elements such as germanium, silicon and the like while growing to achieve N-type doping, and the P-type gallium nitride layer (5) is doped with magnesium elements while growing to achieve P-type doping. The P-type gallium nitride layer metal electrode (6) and the N-type gallium nitride layer metal electrode (7) of the gallium nitride LED are multi-layer structures, which are respectively ITO (indium tin oxide) and other metals or Cr and other metals from bottom to top.

7. The gallium nitride LED and germanium PD monolithic heterogeneous integrated structure according to claim 3, characterized in that: The N-type germanium layer (8) of the germanium photodetector is grown by MOCVD or MBE, and its doping can be achieved by doping with group V elements during growth or by ion implantation of group V elements after growth. The P-type germanium layer (9) of the germanium photodetector is grown by MOCVD or MBE, and its doping can be achieved by doping with group V elements during growth or by ion implantation of group III elements after growth.

8. The gallium nitride LED and germanium PD monolithic heterogeneous integrated structure according to claim 3, characterized in that: The metal contact of the germanium photodetector is a multi-layer structure of ITO / TaN / TiNx / WNx / a-Ge / GeONx / GeSnOx and other metals.

9. The gallium nitride LED and germanium PD monolithic heterogeneous integrated structure according to claim 4, characterized in that: The Schottky contact (91) of the P-type germanium layer of the germanium photodetector is Al or NiGe.

10. A method for preparing a monolithic heterogeneous integrated structure of gallium nitride LED and germanium PD, characterized in that: The following steps are involved: Step 1: Select a silicon substrate layer (1) and clean pollutants on the surface of the silicon substrate layer (1); Step 2: sequentially growing a buffer layer (2), an N-type gallium nitride layer (3), a multi-quantum well light-emitting layer (4), and a P-type gallium nitride layer (5); Step 3: Grooving the structural part obtained in step 2, sequentially growing germanium epitaxial materials, and doping germanium during the growth to obtain an N-type germanium layer (8) and a P-type germanium layer (9) of the germanium photodetector; Step 4: preparing a P-type gallium nitride layer metal electrode (6) and an N-type gallium nitride layer metal electrode (7); Step 5: Prepare a P-type germanium metal electrode (10) and an N-type germanium metal electrode (11) on the germanium material obtained in step 4.

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