A graphene / black silicon composite structure photodetector structure

Abstract

The application discloses a graphene / black silicon photoelectric composite detector structure which integrates advantages of black silicon and graphene, and belongs to the technical field of photoelectric detection. The graphene / black silicon photoelectric composite detector structure comprises a Si substrate (5), a heavily doped layer (3) located on the surface of the Si substrate (5), a graphene layer (2) located above the heavily doped layer (3), an upper electrode (1) arranged on the upper surface of the graphene layer (2), and a metal lower electrode (4) covering the lower surface of the Si substrate (5); and the graphene layer (2) and the upper electrode (1) form an ohmic contact. The graphene / black silicon photoelectric composite detector structure solves the problems of low carrier extraction efficiency of a traditional black silicon photoelectric detector and limited wavelength detection range of a traditional silicon photoelectric detector, and can improve the performance of a silicon-based detector.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photoelectric detection, and particularly relates to a graphene / black silicon photoelectric detector structure. BACKGROUND

[0002] In recent years, with the continuous maturity of research and development of photoelectric detectors, the development of traditional photoelectric detectors based on semiconductor materials such as silicon and germanium has encountered a bottleneck in the expansion of the response band, so it is particularly urgent to find new materials or structures for photoelectric detection technology. Among them, graphene has Π electrons in the basal plane that can move freely, with an electron mobility much higher than that of silicon, and a single-layer graphene has an optical absorption rate of only 2.3%, so it is often used as a transparent conductive film in photoelectric detector devices. When graphene is used as a detector material, it has a high response to weak light, but as the detection light power increases, the graphene detector is easily saturated, and the response is greatly reduced. In order to solve these problems, photoelectric detectors with graphene and other material composite structures have also been developed, which use the substrate for light absorption. Among them, graphene / silicon photoelectric detectors have the highest photoelectric conversion efficiency, so they have good potential. Black silicon has a light absorption rate of more than 90% in the range of 250 nm to 2500 nm, almost covering the entire visible and near-infrared band, and has extremely important potential application value in the field of photoelectric detection and is widely used in silicon-based infrared detection field research, and has achieved a series of outstanding research results. Further, through surface passivation and other treatments, the black silicon photoelectric detector realizes infrared response comparable to commercial germanium detectors under the same working bias.

[0003] Through some existing research, it can be found that the traditional graphene / silicon photoelectric detector has high response, but the band gap of silicon material is large (1.12 eV), and the traditional graphene / silicon photoelectric detector mainly relies on silicon material for light absorption, and graphene is only used as a transparent electrode with high mobility. The response to light with a wavelength of more than 1000 nm is very low, and it is generally not used for infrared band light detection. While the traditional black silicon photoelectric detector has a wide detection range, but the carrier mobility in black silicon is low, the lifetime is short, and the dark current generated by the surface carrier recombination is large, which limits the improvement of the response. Therefore, it is of great significance to expand the detection range of the photoelectric detector while realizing high response and response speed through certain specific methods.

[0004] In order to solve the above problems, the application provides a graphene / black silicon photoelectric composite detector structure. Compared with black silicon detectors and graphene / silicon photoelectric detectors, this photoelectric detector has the advantages of wide response range, high response, and fast response speed. SUMMARY

[0005] The purpose of the present application is to provide a new graphene / black silicon photoelectric composite photodetector structure based on black silicon photodetectors and graphene / silicon photodetectors, which realizes the improvement of the overall performance of the photodetector by taking advantage of the high transmittance and high carrier mobility of graphene and the absorption characteristics of the black silicon surface doping layer to infrared light.

[0006] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0007] A graphene / black silicon composite photodetector structure comprises a Si substrate, a heavily doped layer on the surface of the silicon substrate, a graphene layer above the heavily doped layer, an upper electrode arranged on the upper surface of the graphene layer, and a metal lower electrode covering the lower surface of the entire Si substrate, and the graphene layer and the upper electrode form an ohmic contact.

[0008] In the present application, the heavily doped layer is obtained by irradiating silicon in a doping element-containing atmosphere by femtosecond / nanosecond laser, or by irradiating silicon with a surface vapor-deposited doping element-containing material by femtosecond / nanosecond laser, or by ion implantation, and then activating the impurity atoms in the heavily doped black silicon by rapid thermal annealing to greatly increase the carrier concentration and repair the lattice damage and defects.

[0009] In the present application, the graphene layer is prepared by chemical vapor deposition and then transferred to the light-absorbing surface of the sixth group element heavily doped black silicon by means of polymethyl methacrylate (PMMA).

[0010] In the present application, the upper electrode and the lower electrode are metal thin film electrodes and should form an ohmic contact with graphene, and the metal material is aluminum (Al), gold (Au) or gold-chromium alloy (Au / Cr).

[0011] The working principle of the present application is that the measured light is incident on the surface of the graphene / black silicon composite photodetector, a part of the valence electrons in the black silicon will transition to the conduction band after absorbing enough photon energy to form electron-hole pairs. The electron-hole pairs are separated under the action of the built-in electric field, the holes move in the same direction as the built-in electric field, and the electrons move in the opposite direction of the built-in electric field, and are transmitted to the external circuit by the upper and lower electrodes through the graphene layer and the black silicon interior, respectively, to form a photo-generated current.

[0012] Compared with the prior art, the present application has the following effective effects:

[0013] 1. The present application uses graphene as a transparent electrode, which increases the contact between the electrode and the microstructure of the black silicon surface, is conducive to the collection of photo-generated carriers, partially offsets the influence of the low carrier mobility and short lifetime of the black silicon on the responsivity, and thus improves the performance of the traditional black silicon photodetector.

[0014] 2. The present invention utilizes the characteristic of black silicon that its absorption rate for light in the range of 250nm to 2500nm is as high as over 90%, which almost covers the entire visible light band and near-infrared band, thereby broadening the detection wavelength range based on the graphene / silicon detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a flow chart of the preparation of the graphene / black silicon composite photodetector of the present invention.

[0016] Figure 2 3D structural diagram of the graphene / black silicon composite photodetector of the present invention;

[0017] Figure 2 In the figure, 1 is the metal upper electrode, 2 is the graphene layer, 3 is the black silicon layer heavily doped with sulfur, 4 is the metal lower electrode, and 5 is the single crystal silicon substrate. DETAILED DESCRIPTION

[0018] The following will clearly and comprehensively describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0019] like Figure 2 As shown, the structure comprises an N-type Si substrate, a heavily sulfur-doped layer, a graphene layer, a metal top electrode, and a metal bottom electrode. The N-type Si substrate can be a high-resistance Si single crystal. The heavily sulfur-doped layer is obtained by femtosecond laser irradiation of N-type single crystal silicon in sulfur hexafluoride (SF6) gas at a specific pressure, followed by rapid thermal annealing. The graphene layer is deposited by chemical vapor deposition and then transferred to the light-absorbing surface of the heavily sulfur-doped black silicon using polymethyl methacrylate (PMMA). This graphene / black silicon photodetector structure, with both graphene and black silicon layers, exhibits high responsivity, fast response speed, and a wide detection range.

[0020] The above are only representative embodiments of the present invention in many specific application scopes and do not constitute any limitation on the protection scope of the present invention. Any technical solutions formed by transformation or equivalent replacement fall within the scope of protection of the present invention.

Claims

1. A graphene / black silicon photoelectric composite detector structure, characterized in that: From bottom to top, the structure comprises a metal lower terminal electrode (4) covering the entire lower surface of the Si substrate (5), a Si substrate (5), a heavily doped layer (3) located on the surface of the Si substrate (5), a carrier transmission channel contact structure located above the heavily doped layer (3) and naturally formed by chemical vapor deposition covering the entire black silicon cone-shaped microstructure heavily doped layer region, a single-layer graphene layer (2) used to offset the defects of low carrier mobility and short life of the internal black silicon and serving as a transparent electrode, a metal upper terminal electrode (1) arranged on the upper surface of the single-layer graphene layer (2), and an ohmic contact is formed between the single-layer graphene layer (2) and the upper terminal electrode (1).

2. The graphene / black silicon composite photodetector structure according to claim 1, characterized in that: A graphene layer (2) serving as a transparent electrode is prepared on a light-absorbing surface of a heavily doped black silicon layer (3) by chemical vapor deposition and then transferred with the aid of polymethyl methacrylate (PMMA).

3. The graphene / black silicon photoelectric composite detector structure according to claim 1, characterized in that: A metal upper electrode (1) is prepared by vapor deposition on the graphene layer (2) and forms an ohmic contact with the graphene. The metal material is aluminum, gold or a gold-chromium alloy.

4. The graphene / black silicon composite photodetector structure according to claim 1, characterized in that Heavy doping is achieved by irradiating silicon with a femtosecond / nanosecond laser in an atmosphere containing doping elements, or by irradiating silicon with a doping element material evaporated on the surface with a femtosecond / nanosecond laser, or by ion implantation.

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