CN110148642B - Concave array of graphene-metal heterojunction photodetectors - Google Patents

Abstract

The invention discloses a graphene-metal heterojunction photoelectric detector of a concave array, which can increase a light receiving surface, increase the absorption of graphene to light and avoid damage to the graphene caused by a transfer process. The graphene-metal heterojunction photoelectric detector of the concave array comprises a substrate; an insulating layer, a growth layer and a graphene layer are sequentially arranged on the substrate from bottom to top; the substrate is provided with downward concave grooves distributed in an array manner; the insulation layer is provided with a first convex surface matched with the groove; the growth layer is provided with a second convex surface; a third convex surface is arranged on the graphene layer; an anti-reflection layer is arranged on the inner wall of the inner groove of the third convex surface of the graphene layer; and both sides of the third convex inner groove on the graphene layer are respectively provided with a high work function electrode and a low work function electrode of the wavy interdigital. The graphene-metal heterojunction photoelectric detector adopting the concave array has the characteristics of small volume, high integration level, wide identification range and the like.

Description

Concave array of graphene-metal heterojunction photodetectors

Technical Field

The invention relates to the fields of communication and sensors, in particular to a concave array graphene-metal heterojunction photoelectric detector.

Background technique

As we all know, the principle of photodetectors is that radiation causes the conductivity of the irradiated material to change. Photodetectors are widely used in various fields of military and national economy. In the visible light or near-infrared band, they are mainly used for ray measurement and detection, industrial automatic control, photometry, etc.; in the infrared band, they are mainly used for missile guidance, infrared thermal imaging, infrared remote sensing, etc.

The mainstream structure of current graphene photodetectors is a planar structure, so the light-receiving surface is small, and graphene absorbs less light. In addition, general graphene photodetectors transfer the prepared graphene to the detector substrate, so the graphene is easily damaged during the transfer process.

Summary of the invention

The technical problem to be solved by the present invention is to provide a graphene-metal heterojunction photoelectric detector with a concave array that can increase the light receiving surface, increase the absorption of light by graphene, and avoid damage to the graphene caused by the transfer process.

The technical solution adopted by the present invention to solve the technical problem is: a concave array graphene-metal heterojunction photodetector comprises a substrate; an insulating layer, a growth layer, and a graphene layer are sequentially arranged on the substrate from bottom to top;

The substrate is provided with one or an array of downwardly concave grooves; the insulating layer is provided with a first convex surface that protrudes downward and matches the grooves; the grooves correspond to the first convex surfaces one by one;

The growth layer is provided with a second convex surface which is convex downward and matches the inner groove of the first convex surface; the inner groove of the first convex surface corresponds to the second convex surface one by one;

The graphene layer is provided with a third convex surface which is protruding downward and matches the inner groove of the second convex surface; the inner groove of the second convex surface corresponds to the third convex surface one by one;

An anti-reflection layer is arranged on the inner wall of the inner groove of the third convex surface of the graphene layer; and a wavy interdigitated high work function electrode and a low work function electrode are respectively arranged on both sides of the inner groove of the third convex surface of the graphene layer.

Specifically, the substrate is provided with downwardly recessed grooves distributed in a 3X3 array.

Furthermore, the insulating layer is made of silicon dioxide film.

Preferably, the groove is a hemispherical groove.

Preferably, the growth layer is prepared by first depositing Cu or Au or Ag or Mo or Gr with a thickness of 30 to 70 nanometers, and then depositing Ni with a thickness of 30 to 70 nanometers; or the growth layer is directly deposited as a layer of 30 to 70 nanometers of aluminum oxide.

Furthermore, the graphene layer is a graphene film grown directly on the growth layer by a CVD method; and the number of layers of the graphene film is 1 to 10.

Preferably, the anti-reflection layer is a silicon dioxide film with a thickness of 30 to 100 nanometers.

Specifically, the low work function electrode is made of titanium (Ti), platinum (Pt), manganese (Mn), lithium (Li), or aluminum (Al); and has a thickness of 50 to 100 nanometers.

Specifically, the high work function electrode is made of gold (Au), silver (Ag), nickel (Ni) or palladium (Pd) and has a thickness of 50 to 100 nanometers.

The beneficial effects of the present invention are as follows: the graphene-metal heterojunction photodetector of the concave array described in the present invention has an increased light absorption surface under the same surface area due to the use of a concave structure, and the concave structure can make light reflect multiple times on the graphene surface in the concave surface, increasing the absorption of light by graphene, so relatively speaking, the detector's responsiveness to light is relatively high. Since the growth layer is deposited on the substrate and the graphene film is directly deposited on the surface of the growth layer, the damage to the graphene film caused by the transfer of graphene is avoided, so that the electrical properties of graphene are relatively excellent, which can increase the sensitivity of the photodetector; the electrical properties of graphene are also relatively excellent, and the preparation process is simple, mature and reliable.

Therefore, the concave array graphene-metal heterojunction photodetector of the present invention can quickly detect light signals of different wavelengths and light intensities at room temperature, and has the characteristics of small size, high integration, wide recognition range, etc. In addition, the preparation process of the device is relatively simple and compatible with the existing semiconductor preparation process, and can be mass-produced. It has good application prospects in the fields of light detection and optical communication.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is an exploded schematic diagram of a concave array graphene-metal heterojunction photodetector according to an embodiment of the present invention;

FIG2 is a perspective view of a concave array of graphene-metal heterojunction photodetectors according to an embodiment of the present invention;

FIG3 is a top view of a concave array of graphene-metal heterojunction photodetectors according to an embodiment of the present invention;

Fig. 4 is a cross-sectional view of A-A in Fig. 3;

FIG5 is a cross-sectional view of a single groove of a concave array graphene-metal heterojunction photodetector according to an embodiment of the present invention;

Markings in the figure: 1-substrate, 2-insulating layer, 3-growth layer, 4-graphene layer, 5-anti-reflection layer, 6-high work function electrode, 7-low work function electrode.

Detailed ways

The present invention is further described below in conjunction with the accompanying drawings and embodiments.

As shown in FIGS. 1 to 4 , the concave array graphene-metal heterojunction photodetector of the present invention comprises a substrate 1; an insulating layer 2, a growth layer 3, and a graphene layer 4 are sequentially arranged on the substrate 1 from bottom to top;

The substrate 1 is provided with one or an array of downwardly concave grooves 11; the insulating layer 2 is provided with a first convex surface 21 that bulges downward and matches the grooves 11; the grooves 11 correspond to the first convex surfaces 21 one by one;

The growth layer 3 is provided with a second convex surface 31 which is convex downward and matches the inner groove of the first convex surface 21; the inner groove of the first convex surface 21 corresponds to the second convex surface 31 one by one;

The graphene layer 4 is provided with a third convex surface 41 which protrudes downward and matches the inner groove of the second convex surface 31; the inner groove of the second convex surface 31 corresponds to the third convex surface 41 one by one;

An anti-reflection layer 5 is arranged on the inner wall of the inner groove of the third convex surface 41 of the graphene layer 4 ; and a wavy interdigitated high work function electrode 6 and a low work function electrode 7 are respectively arranged on both sides of the inner groove of the third convex surface 41 of the graphene layer 4 .

Specifically, the insulating layer 2 is made of silicon dioxide film. Specifically, the growth layer is made of Cu or Au or Ag or Mo or Gr deposited first to a thickness of 30 to 70 nanometers, and then Ni is deposited to a growth layer of 30 to 70 nanometers; or the growth layer is directly deposited with a layer of aluminum oxide of 30 to 70 nanometers.

Specifically, the anti-reflection layer 5 is a silicon dioxide film with a thickness of 30 to 100 nanometers.

Specifically, the low work function electrode 7 is made of titanium (Ti), platinum (Pt), manganese (Mn), lithium (Li) or aluminum (Al); and has a thickness of 50 to 100 nanometers.

Specifically, the high work function electrode 6 is made of gold (Au), silver (Ag), nickel (Ni) or palladium (Pd), and has a thickness of 50 to 100 nanometers.

In order to increase the absorption of light by the graphene layer 4, further, the groove 11 is a hemispherical groove.

In order to avoid the transfer of graphene and improve the electrical properties of graphene, the sensitivity of photoelectric detection is improved. Further, the graphene layer 4 is a graphene film directly grown by CVD method; and the number of layers of the graphene film is 1 to 10.

In the concave array graphene-metal heterojunction photodetector described in the present invention, the contact between graphene and the metal electrode can form a contact heterojunction, and the contact between two metals with different work functions and graphene forms two different heterojunctions, and a built-in electric field is formed between the heterojunctions. When light irradiates the graphene surface, the electrons in the graphene absorb the photon energy and thus undergo transitions. As a result, electron-hole pairs, such non-equilibrium photogenerated carriers, are formed in the graphene film. These photogenerated carriers move in a directional manner under the drive of the built-in electric field to form a photocurrent, thereby achieving the purpose of detecting light.

The mainstream structure of current graphene photodetectors is a planar structure, while the concave array graphene-metal heterojunction photodetector described in the present invention adopts a concave structure to increase the light-receiving surface. The concave structure can make light reflect multiple times on the graphene surface in the concave surface, thereby increasing the graphene's absorption of light. In addition, general graphene photodetectors transfer the prepared graphene to the detector substrate, while the present invention directly prepares the graphene film on the growth layer surface of the detector substrate, thereby avoiding the damage to the graphene caused by the transfer process.

Therefore, the concave array graphene-metal heterojunction photodetector of the present invention has the following beneficial effects:

1) The graphene covered on the surface of the concave structure is used as the sensitive material, and the concave structure can make the light reflect multiple times on the graphene surface in the concave surface, thereby increasing the graphene's absorption of light and improving the sensitivity of the photodetector.

2) Depositing a growth layer on the substrate facilitates direct deposition of a graphene film on the detector using the CVD method, thereby avoiding the transfer of graphene and improving the electrical properties of graphene, thereby improving the sensitivity of photoelectric detection.

3) The preparation process is compatible with the existing semiconductor device preparation process, which makes it easy to realize the integrated design and preparation of the detector, greatly improving the practicality of the detector.

4) A concave array structure is adopted to increase the light-receiving surface of the detector. The asymmetric wavy interdigital electrodes in contact with graphene can fully increase the active area of graphene, thereby further increasing the sensitivity of the detector.

Example

As shown in FIGS. 1 to 4 , the concave array graphene-metal heterojunction photodetector comprises a substrate 1; an insulating layer 2, a growth layer 3, and a graphene layer 4 are sequentially arranged on the substrate 1 from bottom to top;

The substrate 1 is provided with a groove 11 which is sunken downwards; the insulating layer 2 is provided with a first convex surface 21 which is protruded downwards and matches the groove 11;

The growth layer 3 is provided with a second convex surface 31 which bulges downward and matches the inner groove of the first convex surface 21; the graphene layer 4 is provided with a third convex surface 41 which bulges downward and matches the inner groove of the second convex surface 31;

An anti-reflection layer 5 is disposed on the inner wall of the inner groove of the third convex surface 41 of the graphene layer 4 ; a high work function electrode 6 and a low work function electrode 7 are disposed on both sides of the groove 11 on the substrate 1 .

The insulating layer 2 is made of silicon dioxide film. The groove 11 is a hemispherical groove. The growth layer is made of Cu or Au or Ag or Mo or Gr deposited first, with a thickness of 30 to 70 nanometers, and then Ni deposited, with a thickness of 30 to 70 nanometers; or the growth layer is directly deposited with a layer of aluminum oxide with a thickness of 30 to 70 nanometers.

The graphene layer 4 is a graphene film directly grown by CVD method; and the number of layers of the graphene film is 1 to 10. The anti-reflection layer 5 is a silicon dioxide film with a thickness of 30 to 100 nanometers. The low work function electrode 7 is made of titanium (Ti), platinum (Pt), manganese (Mn), lithium (Li) or aluminum (Al); the thickness is 50 to 100 nanometers. The high work function electrode 6 is made of gold (Au), silver (Ag), nickel (Ni) or palladium (Pd), and the thickness is 50 to 100 nanometers.

The following processes are used in the specific preparation process:

1) Using photolithography technology, a 3×3 array of circular holes with a diameter of 5 to 10 microns is made on the surface of the substrate 1;

2) A concave structure is processed on the surface of the silicon substrate 1 by using plasma etching (ICP) or hydrofluoric acid, and then the surface photoresist is removed. The depth of the concave surface is about 1 micron.

3) A layer of silicon dioxide film is deposited as the insulating layer 2 on the silicon wafer with the concave surface processed by magnetron sputtering process, and the thickness of the silicon dioxide is about 50 to 100 nanometers.

4) A growth layer 3 (an alloy of one of the metals Cu, Au, Ag, Mo, Gr and Ni) is deposited on the silicon dioxide insulating layer by a magnetron sputtering process, wherein Cu or Au or Ag or Mo or Gr is first deposited to a thickness of about 50 nanometers, and then Ni is deposited to a thickness of about 50 nanometers; or a layer of aluminum oxide of 30 to 70 nanometers is directly deposited on the growth layer.

5) A graphene layer 4 is directly grown on the surface of the growth layer 3 deposited in step 4 by using a CVD method.

6) Asymmetric active metal low work function electrodes 7: titanium (Ti), platinum (Pt), manganese (Mn), lithium (Li), aluminum (Al) and high work function electrodes 6: gold (Au), silver (Ag), nickel (Ni), palladium (Pd) are deposited on both ends of the graphene using photolithography technology and magnetron sputtering process. The thickness of the electrodes is 50 to 100 nanometers, and then the surface photoresist is removed.

7) A layer of anti-reflection film 5 (silicon dioxide) is deposited on the concave surface of the graphene by using photolithography technology and magnetron sputtering process, the thickness of the silicon dioxide is 30 to 100 nanometers, and then the surface photoresist is removed.

Specifically, the photolithography process (negative photoresist RPN-1150) is carried out using the following process:

1. Glue application;

A layer of photoresist was spin-coated on the surface of the sample using a coating machine. The speed of the coating machine was set to: first, low speed (1000 rpm) for 10 s, then high speed (3000 rpm) for 40±2 s; the thickness of the photoresist after spin coating was 2.5±0.05 μm;

2. Pre-baking;

Before coating, turn on the hot plate power switch and set the heating temperature to 90±2℃; after the temperature stabilizes, place the sample coated with photoresist on the hot plate and bake for 90±1s;

3. Exposure;

Turn on the power switch of the photolithography machine, turn on the mercury lamp to preheat for more than 20 minutes, install the mask on the mask fixture, place the dried sample on the sample tray, move the sample tray to align the sample with the pattern on the mask, set the exposure time to 7.5±0.5s after completing the plate alignment, and start exposure;

4. Post-baking;

Set the hot plate temperature to 110±2℃. After the temperature stabilizes, place the exposed sample on the hot plate and bake for 60±10s. Then quickly remove the sample from the hot plate.

5. Development;

Place an appropriate amount of RZX-3038 developer in a clean petri dish, place the post-baking sample in the developer for 50±2s, then rinse the sample with deionized water for several times, and finally blow dry the sample with a N2 gun;

6. Ultraviolet ozone cleaning treatment;

Place the developed sample into the chamber of the UV ozone cleaning machine (BZS250GF-TC), turn on the power switch, set the degumming time to 3 to 5 minutes, turn on the UV light switch, and start removing the residual glue in the graphic area;

7. Hard membrane;

Place the sample that has been cleaned with UV-ozone on a hot plate at a temperature of 110±2°C and bake it for 5 to 15 minutes. After baking, turn off the power of the hot plate and take samples.

Specifically, the magnetron sputtering is performed using the following process:

Magnetron sputtering is a type of physical vapor deposition (PVD). The general sputtering method can be used to prepare multiple materials such as metals, semiconductors, insulators, etc., and has the advantages of simple equipment, easy control, large coating area and strong adhesion. The present invention mainly uses this method to sputter silicon dioxide insulation layer, growth layer, electrode, silicon dioxide anti-reflection film. The experimental steps are as follows:

1. Turn on the device;

Turn on the power switch of the air compressor and its gas line valve; turn on the power switch of the chiller; open the valve of the protective gas cylinder; press the "total power start" button on the control panel, press the "total power start" button; press the "RF power start button" or "DC power start button"; open the control software, make sure the vacuum gauge is turned off, click the "inflation valve", inflate the chamber, and wait for the inflation to be completed;

2. Target loading and setting out;

Press and hold the "Up" button until the indicator light next to the Up button turns green; in the baffle control panel, select the desired target position, open the baffle, and replace the target material; after replacing the target material, select the sputtering mode: direct target sputtering, manually adjust the target position, and manually adjust the baffle when the baffle is closed to ensure that the baffle blocks the sputtering target position; according to the selected sputtering mode, put in the sample; press and hold the "Down" button until the indicator light next to it turns green, and ensure that the top cover is closed and the chamber observation window is closed;

3. Vacuuming;

Click "Mechanical Pump" on the control panel, click "Fore Valve", wait for tens of seconds, then click the molecular pump. After the molecular pump starts to rotate, close the "Fore Valve" and open the "Pre-pump Valve". When the chamber pressure drops below 3.5Pa, open the "Vacuum Gauge", close the "Pre-pump Valve", open the "Fore Valve", and open the "Plug Valve"; when the chamber pressure drops below 5Pa, click to close the vacuum gauge, and then introduce the required gas into the chamber by clicking "Vpg1", "Vpg2", and "Vpg3";

4. Sputtering;

In the working pressure control panel, enter the ignition pressure: 5±0.5Pa, click OK, and after the pressure reaches the setting, enter the ignition value, and then click the "Open" button to observe whether plasma is generated at the target position; after plasma is generated, further adjust the sputtering background pressure to 0.8±0.1Pa; after the plasma is stable, pre-sputter for about 5 minutes, then open the baffle for sputtering, record the time, and after 30±3 minutes, close the baffle of the sputtering target to stop sputtering;

5. Sampling;

Click the "Off" button on the power panel to turn off the power, enter the gas flow value as 0, and then turn off "Vpg"; close the "gate valve", click the "deflation valve" to inflate the chamber; after the inflation is completed, take out the sample.

Specifically, the CVD method for preparing graphene is carried out using the following process:

CVD is the abbreviation of Chemical Vapor Deposition, which refers to a gas phase reaction at high temperature, such as thermal decomposition of metal halides, organic metals, hydrocarbons, etc., hydrogen reduction or a method of causing a mixed gas thereof to undergo a chemical reaction at high temperature to precipitate inorganic materials such as metals, oxides, and carbides. The present invention grows graphene on the surface of a growth layer, deposits a layer of Ni on Mo or Cu or Au or Ag or Gr, or directly deposits a layer of 30 to 70 nanometers of aluminum oxide as a growth layer. Then, a low-pressure CVD method is used to prepare graphene, and finally a few layers of graphene film are directly generated on the surface of the growth layer. The experimental steps are as follows:

1. Pretreatment of the growth layer: wipe the surface of the growth layer with acetone and anhydrous ethanol in turn, then place the sample in a culture dish filled with deionized water for 3 to 5 minutes, and finally use a nitrogen gun to blow dry the sample.

2. Place the sample into the reaction chamber (2-inch quartz tube); place the processed sample on the quartz boat, use a glass rod to move the quartz boat from one end of the quartz tube into the appropriate position of the quartz tube (the heating temperature zone of the tube furnace), and then seal the quartz tube.

3. Set the growth parameters; mainly set the heating temperature and gas flow rate of the two-zone tube furnace. The temperature parameters mainly include the heating time, temperature, and holding time in the annealing stage, and the temperature and holding time in the growth stage; the gas parameters mainly include the flow rates of hydrogen, argon, and methane.

4. Vacuuming: Use a mechanical pump to continuously evacuate for 5 to 10 minutes. When the pressure in the reaction chamber is lower than 0.1 Pa, proceed to the next step.

5. Heating annealing: introduce protective gas, a mixture of argon and hydrogen, with a flow rate of 100 sccm. Turn on the heating switch of the tube furnace, raise the temperature to 900°C and maintain constant temperature for annealing for 30 minutes.

6. Graphene growth: After annealing, the mixture of argon and hydrogen is changed to hydrogen with a flow rate of 100 sccm; the tube furnace is heated to 1000°C and kept at a constant temperature, and then methane is introduced with a flow rate of 5 to 30 sccm to start the growth of graphene. The growth time is 15 to 60 minutes.

7. Cooling and sampling: After the graphene growth is completed, turn off the methane first, then exit the heating program and stop heating, then open the top cover of the tubular furnace to quickly cool down, and keep hydrogen in during the cooling process. When the temperature of the tubular furnace chamber drops below 50°C, turn off the hydrogen and stop vacuuming, and finally break the vacuum to take out the sample.

Specifically, plasma etching (ICP) adopts the following process:

ICP is the abbreviation of plasma etching, which is one of the etching processes for making semiconductor integrated circuits. When removing the unnecessary protective film on the integrated circuit board, the ion beam of reactive gas is used to cut the chemical bonds of the protective film material, so that low molecular weight substances are produced, which volatilize or free from the board surface. This method is called reactive ion etching. The present invention uses this method to etch silicon, so that the surface of silicon forms a concave surface, increasing the light-receiving surface. The specific experimental steps are as follows:

(1) Preparation;

Before the experiment, first check whether all parts of the machine are in good condition. If there are no problems, open the cooling water tank first, then turn on the main power switch at the bottom of the electrical control cabinet, and prepare for the experimental operation.

(2) Installing samples;

Press the switch of the etching chamber inflation valve VINC of the central control system to fill air into the etching chamber. After 4 minutes of inflation, the lifting and lowering permission indicator light comes on. Press the raising button to lift the upper cover, place the target sample on the electrode, press the lowering button, the upper cover falls down and closes the inflation valve VINC.

(3) Vacuuming;

Turn on the power of the vacuum gauge, turn on the mechanical pump RPC, and pre-pump the molecular pump. After the mechanical pump has been running for about 2 minutes, turn on the molecular pump (confirm whether the cooling water of the molecular pump is introduced), wait for the molecular pump to operate normally, open the pre-pumping valve VPRC, and after the vacuum degree reaches 2Pa, open the gate valve to pump the vacuum chamber to high vacuum.

(4) Turn on both RF power switches and preheat for 5 minutes.

(5) introducing reaction gas;

After the etching chamber is evacuated to the background vacuum (generally 3.0×10-3Pa or higher), close the vacuum gauge measurement switch, introduce the reaction gases SF630sccm and O230sccm, open the air inlet manual valve to allow the reaction gases to enter the vacuum chamber, then open the vacuum gauge, turn off the high vacuum, and after the flow rate stabilizes, adjust the vacuum chamber working pressure to 1Pa by manually adjusting the gate valve opening.

(6) Etching;

First, confirm whether the electrode cooling water is flowing. After the vacuum chamber pressure is stable, turn on the RF power supply W1, rotate the plate pressure knob clockwise to ignite the etching chamber, adjust the power to 300W, and adjust the "C1 adjustment" and "C2 adjustment" on the matching box at the same time to make the effective power as large as possible and the reflected power as small as possible to achieve a good match. Turn on the RF power supply W2, adjust the power to 100W, adjust the match, and start timing.

(7) Sampling;

Turn off the W2 and W1 plate pressures in turn, turn off the mass flow meter, and close the air inlet manual valve. Open the gate valve and extract the residual gas in the etching chamber for a while. Close the gate valve VG, open the inflation valve VINL, and wait until the yellow lifting and lowering permission indicator on the central control system panel lights up (about 4 minutes), lift the upper cover, take out the sample, cover the upper cover, close VINL, exhaust the reaction gas in the pipeline, pump the reaction chamber to high vacuum, and close the gate valve. Turn off the molecular pump, and the mechanical pump continues to run for 15 minutes. After the molecular pump stops working, turn off the mechanical pump. Turn off the switches of each instrument, turn off the cooling water, and turn off the reaction gas source switch.

Claims (7)

1. The graphene-metal heterojunction photoelectric detector of the concave array is characterized in that: comprising a substrate (1); an insulating layer (2), a growth layer (3) and a graphene layer (4) are sequentially arranged on the substrate (1) from bottom to top;

The substrate (1) is provided with one or an array of downward concave grooves (11); a first convex surface (21) which protrudes downwards and is matched with the groove (11) is arranged on the insulating layer (2); the grooves (11) are in one-to-one correspondence with the first convex surfaces (21);

A second convex surface (31) which protrudes downwards and is matched with the inner groove of the first convex surface (21) is arranged on the growth layer (3); the inner grooves of the first convex surfaces (21) are in one-to-one correspondence with the second convex surfaces (31);

A third convex surface (41) which protrudes downwards and is matched with the inner groove of the second convex surface (31) is arranged on the graphene layer (4); the inner grooves of the second convex surfaces (31) are in one-to-one correspondence with the third convex surfaces (41);

An anti-reflection layer (5) is arranged on the inner wall of the inner groove of the third convex surface (41) of the graphene layer (4); both sides of the groove in the third convex surface (41) on the graphene layer (4) are respectively provided with a high work function electrode (6) and a low work function electrode (7) which are of wave-shaped interdigital;

the substrate (1) is provided with downward concave grooves (11) distributed in a 3X3 array manner;

The growth layer is formed by depositing Cu or Au or Ag or Mo or Gr with the thickness of 30-70 nanometers, and then depositing Ni with the thickness of 30-70 nanometers; or a layer of 30 to 70 nm of aluminum oxide deposited directly on the growth layer.

2. The concave array graphene-metal heterojunction photodetector of claim 1, wherein: the insulating layer (2) is made of a silicon dioxide film.

3. The concave array graphene-metal heterojunction photodetector of claim 1, wherein: the groove (11) is a hemispherical groove.

4. The concave array graphene-metal heterojunction photodetector of claim 1, wherein: the graphene layer (4) is a graphene film directly grown on the growth layer (3) by adopting a CVD method; and the number of layers of the graphene film is 1-10.

5. The concave array graphene-metal heterojunction photodetector of claim 4, wherein: the anti-reflection layer (5) is a silicon dioxide film with the thickness of 30-100 nanometers.

6. The concave array graphene-metal heterojunction photodetector of claim 5, wherein: the low work function electrode (7) adopts titanium (Ti), platinum (Pt), manganese (Mn), lithium (Li) or aluminum (Al); the thickness is 50-100 nanometers.

7. The concave array graphene-metal heterojunction photodetector of claim 6, wherein: the high work function electrode (6) adopts gold (Au), silver (Ag), nickel (Ni) or palladium (Pd) with the thickness of 50-100 nanometers.