Graphene-hafnium oxide interface layer-germanium heterojunction photoelectric detector and preparation method thereof
By introducing a hafnium oxide interface layer on the germanium sheet and forming a graphene-hafnium oxide interface layer-germanium heterojunction structure, the problem of high dark current of the existing graphene/germanium photodetectors is solved, and dark current is reduced and information is improved. The effects of noise ratio and detection sensitivity.
Patent Information
- Application Number
- CN202411636407.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-15
- Publication Date
- 2025-02-21
AI Technical Summary
The existing graphene/germanium photodetectors have a lower signal-to-noise ratio due to the presence of high dark currents, which affects the detection ability of weak signals and increases power consumption and noise.
By introducing a hafnium oxide interface layer on the germanium sheet and forming a graphene-hafnium oxide interface layer-germanium heterojunction structure on it, the high dielectric constant material characteristics of hafnium oxide are used to improve the interface characteristics and reduce interface defects and carriers. recombination, thereby reducing dark current.
It effectively reduces the dark current of the photodetector, improves the signal-to-noise ratio and detection sensitivity, improves the photoelectric response performance, simplifies the preparation process, and reduces costs.
Smart Images
Figure CN119497462A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of photoelectric detection technology, in particular to a graphene-hafnium oxide interface layer-germanium heterojunction photoelectric detector and a preparation method thereof. Background Art
[0002] In the visible and near-infrared bands, photodetectors are mainly used in radiation measurement, industrial automation control, and photometry, while in the infrared band, the application of photodetectors is concentrated in missile guidance, infrared thermal imaging, and infrared remote sensing. Germanium (Ge), as a key semiconductor material, is one of the important substrate materials in photodetectors. Germanium-based photodetectors show good response performance in the visible and near-infrared bands.
[0003] However, current graphene / germanium photodetectors face a major problem, namely the presence of high dark current. Dark current refers to the current that still exists inside the device in the absence of light. This phenomenon can significantly reduce the signal-to-noise ratio of the photodetector, thereby affecting its ability to detect weak signals. In addition, higher dark currents can also lead to increased device power consumption and increased noise levels, limiting their effectiveness in practical applications. Summary of the invention
[0004] In view of the problem that the detection capability of photodetectors in the prior art is limited due to the presence of high dark current, the present invention provides a graphene-hafnium oxide interface layer-germanium heterojunction photodetector and a preparation method thereof.
[0005] The present invention is achieved through the following technical solutions: A method for preparing a graphene-hafnium oxide interface layer-germanium heterojunction photoelectric detector comprises the following steps: Step 1, cleaning the germanium sheet to obtain a pre-treated germanium sheet; Step 2, sputtering a hafnium oxide film on the surface of the pretreated germanium wafer by vacuum thin film sputtering to obtain a preliminary product containing a hafnium oxide interface layer; Step 3, sputtering and growing an insulating layer and a positive electrode on the hafnium oxide interface layer of the preliminary product to obtain a secondary product; Step 4, turning over the secondary product, and sputtering a back electrode on the back of the secondary product to obtain a tertiary product; Step 5, transferring the single-layer graphene to the positive electrode of the tertiary product by electrochemical bubbling method to obtain a crude product; Step 6, annealing the rough product to obtain a graphene-hafnium oxide interface layer-germanium heterojunction photodetector.
[0006] Preferably, in step 1, the specific steps of cleaning the germanium sheet are: ultrasonically cleaning the germanium sheet with no damage on the surface with acetone, anhydrous ethanol, and deionized water in sequence, then immersing the germanium sheet in 2% hydrofluoric acid and 15% hydrochloric acid in sequence for cleaning, then rinsing it with deionized water, and finally drying it and storing it under vacuum.
[0007] Preferably, in step 2, the sputtering conditions of the hafnium oxide film are: the vacuum degree is 1×10 -3 Pa, sputtering is carried out under inert gas conditions, the sputtering power is 60~80W, and the sputtering time is 1~5min.
[0008] Preferably, in step 3, the grown insulating layer and the positive electrode are sputtered using high-purity target materials of aluminum oxide and titanium, respectively, wherein the sputtering power of aluminum oxide is 80-110 W, and the sputtering time is 30-60 min; the sputtering power of the positive electrode is 40-70 W, and the sputtering time is 5-20 min.
[0009] Preferably, in step 4, the back electrode is sputtered using a high-purity target material titanium, the sputtering power is 40-70 W, and the sputtering time is 5-20 min.
[0010] Preferably, both the back electrode and the positive electrode can be one or a composite electrode of several of gold, silver, titanium, aluminum and indium gallium alloy.
[0011] Preferably, in step 5, graphene is grown by chemical vapor deposition.
[0012] Preferably, in step 5, the graphene transfer process is: first prepare a PMMA solution, then apply the PMMA solution on the cut graphene / copper foil sheet, then solidify the PMMA solution, and then use a bubbling method to transfer the graphene to the substrate, wait for the water to evaporate basically before heating, and then use acetone, alcohol, and deionized water to soak and remove PMMA in turn, and finally dry it to complete the transfer.
[0013] Preferably, in step 6, the annealing temperature is 350° C. to 450° C., and the annealing time is 30 to 60 min.
[0014] A photoelectric detector obtained according to the method for preparing a graphene-hafnium oxide interface layer-germanium heterojunction photoelectric detector.
[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a method for preparing a graphene-hafnium oxide interface layer-germanium heterojunction photodetector. A hafnium oxide interface layer is introduced between germanium and graphene. Hafnium oxide is used as a high dielectric constant material to effectively improve the interface characteristics of the device, reduce interface defects and carrier recombination, and thus effectively reduce dark current. The dark current of the photodetector is reduced to enhance the detection of weak signals, and the switching ratio can be improved at the same time. The method of the present invention has a simple process, low cost, and is easy to promote. At the same time, because graphene has extremely high carrier mobility and good optical transparency, it can quickly respond to light signals in the photodetector. By combining graphene with germanium, a highly sensitive photodetector can be realized. The introduction of the hafnium oxide layer not only optimizes the interface properties, but also enhances the interface bonding force between graphene and germanium, and improves the photoelectric response performance.
[0016] Furthermore, the preparation process used in this method is relatively simple, and is mainly achieved through mature technologies such as chemical vapor deposition (CVD) and magnetron sputtering or atomic layer deposition. These processes are highly repeatable and low-cost, are easy to mass produce, and have good industrial prospects. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 It is a flow chart of the method for preparing the graphene-hafnium oxide interface layer-germanium heterojunction photoelectric detector of the present invention; Figure 2 It is a schematic structural diagram of a photoelectric detector obtained by a method for preparing a graphene-hafnium oxide interface layer-germanium heterojunction photoelectric detector of the present invention; Figure 3 It is a comparison diagram of the dark current of the photodetector before and after the oxide interface layer is introduced in the present invention.
[0018] In the figure, 1. back electrode; 2. germanium sheet; 3. oxide interface layer; 4. insulating layer; 5. positive electrode; 6. graphene layer. DETAILED DESCRIPTION
[0019] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.
[0020] The present invention discloses a method for preparing a graphene-hafnium oxide interface layer-germanium heterojunction photoelectric detector, referring to Figure 1 , 2 , including the following steps: Step 1, cleaning the germanium sheet to obtain a pretreated germanium sheet, specifically: ultrasonically cleaning the germanium sheet with no damage on the surface with acetone, anhydrous ethanol, and deionized water for 10 to 20 minutes in sequence to remove surface organic matter and impurities, then immersing the cleaned germanium sheet in 2% hydrofluoric acid and 15% hydrochloric acid for 5 minutes each to remove the natural oxide layer on the surface, then rinsing it with deionized water, and finally drying it and storing it in a vacuum.
[0021] Step 2: Sputtering a hafnium oxide thin film on the surface of the pretreated germanium wafer by vacuum thin film sputtering to obtain a preliminary product containing a hafnium oxide interface layer, specifically: placing the treated substrate into a growth tray and then into a sputtering chamber and closing it, and evacuating the chamber to a vacuum of 1×10 -3 Pa, introduce argon gas, set the argon flow rate to 20-40sccm, use high-purity hafnium oxide target material for thin film sputtering under argon atmosphere, sputtering power is 60-80W, sputtering time is 1-5min. Turn on the self-rotating motor during sputtering to ensure uniform film.
[0022] Step 3, sputtering an insulating layer and a positive electrode on the hafnium oxide interface layer of the preliminary product to obtain a secondary product, specifically: placing a customized mask on the germanium substrate containing the interface layer, and using high-purity target materials aluminum oxide and titanium to sputter and grow an insulating layer and a positive electrode. Among them, the aluminum oxide sputtering power is 80~110W, and the sputtering time is 30~60min; the electrode sputtering power is 40~70W, and the sputtering time is 5~20min.
[0023] Step 4, flip the secondary product over, and sputter a back electrode on the back of the secondary product to obtain a tertiary product, specifically: flip the germanium sheet sputtered in step 3 over and sputter the back electrode, the process parameters are the same as the positive electrode. The back electrode and the positive electrode can be one or a composite electrode of several of gold, silver, titanium, aluminum and indium gallium alloy.
[0024] Step 5: Transfer the graphene to the positive electrode of the tertiary product by electrochemical bubbling method to obtain a crude product.
[0025] Among them, the number of graphene layers is not limited, and the single-layer graphene is grown by chemical vapor deposition method, specifically: cut the copper foil to a suitable size, soak it in 3% ammonium persulfate solution for 5 minutes, soak it in deionized water and shake it, and then clean it with anhydrous ethanol for 5 minutes. Fold the cleaned copper foil and put it in the ark and send it into the CVD quartz tube to start growing graphene. The first stage is the heating stage, setting the target temperature to 1030℃, the heating time to 50min, and passing hydrogen (H2) 10sccm. The second stage is the growth stage, setting the growth temperature to 1030℃, the growth time to 30min, passing hydrogen (H2) 10sccm, and methane (CH4) 10sccm. After the growth stage, stop heating, keep the gas flow rate unchanged, and wait for cooling to room temperature before taking it out for use.
[0026] The transfer process of single-layer graphene is as follows: first, 0.9g of powdered polymethacrylate (PMMA) is dissolved in 30ml of chlorobenzene to prepare a PMMA solution, then the PMMA solution is applied to the cut graphene / copper foil sheet, and then the sheet is dried on a heating table at 120°C for 1h to solidify the PMMA, and then the graphene is transferred to the substrate using the bubbling method, and then the sheet is heated on a heating table at 150°C for 1h after the water is basically evaporated. Then, acetone, alcohol, and deionized water are used to soak for 15min in turn to remove the PMMA, and then the sheet is placed in a drying oven for 20min to complete the transfer.
[0027] Step 6: annealing the crude product in a CVD annealing furnace to obtain a graphene-hafnium oxide interface layer-germanium heterojunction photodetector, wherein the annealing temperature is 350° C. to 450° C. and the time is 30 to 60 minutes. Annealing can reduce the residual amount of chemical substances and improve the photoelectric response characteristics of the device.
[0028] Example 1 Step 1, clean the surface of an undamaged n-type doped germanium substrate with a resistivity of about 1 Ω·cm and blow dry it; Step 2: Place the processed substrate into the growth tray and then into the sputtering chamber, close it, and evacuate the chamber to 1×10 -3 Below Pa, argon gas was introduced with an argon flow rate of 30 sccm. Thin film sputtering was performed using a high-purity hafnium oxide target in an argon atmosphere with a sputtering power of 70 W and a sputtering time of 2 min.
[0029] Step 3: Place a customized mask on the germanium substrate containing the interface layer, and use high-purity target materials aluminum oxide and titanium to sputter and grow the insulating layer and the positive electrode. The aluminum oxide sputtering power is 100W, and the sputtering time is 40 minutes; the electrode sputtering power is 60W, and the sputtering time is 10 minutes; Step 4, sputtering a titanium electrode on the back of the germanium substrate, with the process parameters being consistent with those of the positive electrode; Step 5, transferring the grown single-layer graphene to a germanium substrate containing an interface layer; Step 6, placing the sample in a CVD annealing furnace and annealing at 400° C. for 40 minutes to obtain a graphene / hafnium oxide / germanium photodetector.
[0030] Comparative Example 1 Step 1, clean the surface of an n-type doped germanium substrate with a resistivity of about 3Ω·cm without any damage, and blow dry it; Step 2: Place a customized mask on the germanium substrate and use high-purity target materials of aluminum oxide and titanium to sputter and grow the insulating layer and the positive electrode. The aluminum oxide sputtering power is 100W and the sputtering time is 40 minutes; the electrode sputtering power is 60W and the sputtering time is 10 minutes; Step 3, sputtering a titanium electrode on the back of the germanium substrate, with the process parameters being consistent with those of the positive electrode; Step 4, transferring the grown single-layer graphene to a germanium substrate; Step 5, placing the sample in a CVD annealing furnace and annealing at 400° C. for 40 minutes to obtain a graphene / hafnium oxide / germanium photodetector.
[0031] Example 2 Step 1, clean and dry an n-type doped germanium substrate with a resistivity of about 10Ω·cm without any damage on the surface; Step 2: Place the processed substrate into the growth tray and then into the sputtering chamber, close it, and evacuate the chamber to 1×10 -3 Below Pa, argon gas was introduced with an argon flow rate of 40 sccm. Thin film sputtering was performed using a high-purity hafnium oxide target in an argon atmosphere with a sputtering power of 70 W and a sputtering time of 4 min.
[0032] Step 3: Place a customized mask on the germanium substrate containing the interface layer, and use high-purity target materials silicon dioxide and silver to sputter and grow the insulating layer and the positive electrode. The silicon dioxide sputtering power is 80W, and the sputtering time is 30 minutes; the electrode sputtering power is 50W, and the sputtering time is 10 minutes; Step 4, spin coating a conductive silver paste on the back of the germanium substrate to prepare a back electrode; Step 5, transferring the three layers of graphene to a germanium substrate containing an interface layer; Step 6, placing in a CVD annealing furnace and annealing at 425° C. for 30 min to obtain a graphene / hafnium oxide / germanium photodetector.
[0033] Reference Figure 3 Compared with the graphene-germanium photodetector, the IV curve of the photodetector after the introduction of the hafnium oxide interface layer still retains obvious rectification characteristics, which shows that both detectors have formed a Schottky structure. At the same time, through experimental research, the dark current of the graphene / germanium photodetector without the introduction of the hafnium oxide interface layer in the comparative example is 8.8×10 -4 A, and after the introduction of hafnium oxide (i.e., Example 1), the dark current dropped to 3.5×10 -5 A. This data shows that after the introduction of the hafnium oxide interface layer, due to the existence of the interface layer, electrons are confined to the germanium side, while holes mainly penetrate the interface layer through the tunneling mechanism, effectively reducing the recombination of carriers, reducing the dark current of the photodetector by at least one order of magnitude, greatly improving the detection sensitivity of the device and improving the device's ability to detect weak signals.
[0034] The present invention also discloses a photoelectric detector obtained according to the method for preparing the graphene-hafnium oxide interface layer-germanium heterojunction photoelectric detector, referring to Figure 2The structure is composed of back electrode, germanium sheet, oxide interface layer, insulating layer, positive electrode and graphene layer from bottom to top. The graphene / germanium heterojunction photodetector with hafnium oxide interface layer has shown good feasibility in theory and experiment, and significantly improved the performance of the photodetector, especially in reducing dark current, improving signal-to-noise ratio and enhancing detection sensitivity.
[0035] The above description is only a preferred embodiment of the present invention and is not intended to impose any limitation on the technical solution of the present invention. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can also be subjected to several simple modifications and substitutions, and these modifications and substitutions are also within the scope of protection covered by the claims.
Claims
1. A method for preparing a graphene-hafnium oxide interface layer-germanium heterojunction photodetector, characterized in that: The following steps are involved: Step 1, cleaning the germanium sheet to obtain a pre-treated germanium sheet; Step 2, sputtering a hafnium oxide film on the surface of the pretreated germanium wafer by vacuum thin film sputtering to obtain a preliminary product containing a hafnium oxide interface layer; Step 3, sputtering and growing an insulating layer and a positive electrode on the hafnium oxide interface layer of the preliminary product to obtain a secondary product; Step 4, turning over the secondary product, and sputtering a back electrode on the back of the secondary product to obtain a tertiary product; Step 5, transferring the graphene to the positive electrode of the tertiary product by electrochemical bubbling method to obtain a crude product; Step 6, annealing the rough product to obtain a graphene-hafnium oxide interface layer-germanium heterojunction photodetector.
2. The method for preparing a graphene-hafnium oxide interface layer-germanium heterojunction photodetector according to claim 1, characterized in that: In step 1, the specific steps of cleaning the germanium sheet are: ultrasonically clean the germanium sheet with no damage on the surface with acetone, anhydrous ethanol, and deionized water in turn, then soak the germanium sheet in 2% hydrofluoric acid and 15% hydrochloric acid in turn for cleaning, then rinse it with deionized water, and finally blow dry and store it under vacuum.
3. The method for preparing a graphene-hafnium oxide interface layer-germanium heterojunction photodetector according to claim 1, characterized in that: In step 2, the sputtering conditions of the hafnium oxide film are: the vacuum degree is 1×10 -3 Pa, sputtering is carried out under inert gas conditions, the sputtering power is 60~80W, and the sputtering time is 1~5min.
4. The method for preparing a graphene-hafnium oxide interface layer-germanium heterojunction photodetector according to claim 1, characterized in that: In step 3, the growing insulating layer and the positive electrode are sputtered using high-purity target materials of aluminum oxide and titanium, respectively, wherein the sputtering power of aluminum oxide is 80-110 W, and the sputtering time is 30-60 min; the sputtering power of the positive electrode is 40-70 W, and the sputtering time is 5-20 min.
5. The method for preparing a graphene-hafnium oxide interface layer-germanium heterojunction photodetector according to claim 1, characterized in that: In step 4, the back electrode is sputtered using high-purity target titanium, the sputtering power is 40~70W, and the sputtering time is 5~20min.
6. The method for preparing a graphene-hafnium oxide interface layer-germanium heterojunction photodetector according to claim 1, characterized in that: The back electrode and the positive electrode can be one or a composite electrode of several of gold, silver, titanium, aluminum and indium gallium alloy.
7. The method for preparing a graphene-hafnium oxide interface layer-germanium heterojunction photodetector according to claim 1, characterized in that: In step 5, graphene is grown by chemical vapor deposition.
8. The method for preparing a graphene-hafnium oxide interface layer-germanium heterojunction photodetector according to claim 1, characterized in that: In step 5, the graphene transfer process is: first prepare the PMMA solution, then apply the PMMA solution on the cut graphene / copper foil sheet, then solidify the PMMA solution, and then use the bubbling method to transfer the graphene to the substrate, wait for the water to evaporate basically before heating, and then use acetone, alcohol, and deionized water to soak and remove PMMA in turn, and finally dry it to complete the transfer.
9. The method for preparing a graphene-hafnium oxide interface layer-germanium heterojunction photodetector according to claim 1, characterized in that: In step 6, the annealing temperature is 350° C. to 450° C., and the annealing time is 30 to 60 minutes.
10. A photodetector obtained by the method for preparing a graphene-hafnium oxide interface layer-germanium heterojunction photodetector according to any one of claims 1 to 9.