CN107146830A - A kind of method for the graphene/silicon metal-semiconductor-metal photo detector for preparing flexible and transparent - Google Patents

Abstract

The invention discloses a method for preparing a flexible and transparent graphene/silicon metal-semiconductor-metal photodetector, comprising: etching a silicon thin film of an SOI silicon substrate into silicon strips; The upper surface of the isolation layer is photoetched with gold electrode patterns and gold-plated electrodes; the single-crystal graphene film is prepared; the surface of the silicon dioxide isolation layer, silicon strips and gold electrodes is covered with a single-crystal graphene film; the single-crystal graphene film is patterned into Interdigitated type; cover the PC film on the upper surface of the patterned device, scrape off the edge PC film, put it into the BOE etching solution to etch off the silicon substrate; the photodetector of the present invention can perform wide-spectrum detection, solving the problem of traditional silicon The base PIN junction has the problem of low response to ultraviolet light detection, and the photogenerated carriers and the silicon lattice produce collision ionization to obtain high gain; the preparation process of the invention is simple, the cost is low, and it has high responsivity, fast response speed, and internal gain Large, small switch ratio, easy to integrate.

Description

A flexible and transparent graphene/silicon metal-semiconductor-metal photodetector device method

technical field

The invention belongs to the technical field of photoelectric detection, relates to the structure of a photoelectric detection device, in particular to a method for preparing a flexible and transparent graphene/silicon metal-semiconductor-metal photodetector

Background technique

Good electrical conductivity, high optical transparency and good mechanical flexibility make graphene a promising application prospect for the next generation of flexible electronic devices. Among them, graphene is combined with a semiconductor to form a Schottky junction, which can be applied in the fields of electronics and optoelectronics. While organic semiconductors are inherently flexible, graphene-semiconductor Schottky junctions are ideal for flexible electronics. However, major issues such as poor stability, non-repeatable response, and poor device performance, especially compared with silicon-based devices, limit their wider applications. Furthermore, organic semiconductors have lower mobility compared to single crystal silicon.

As one of the most important semiconductor materials in the twentieth century, silicon has been driving the great success of the electronics, optoelectronics and solar cell industries, mostly in the form of single crystal, polycrystalline silicon wafers and amorphous and nanocrystalline thin films. Silicon is an ideal semiconductor material for photodetectors due to its suitable bandgap structure, mature CMOS fabrication technology, high reliability, well-controlled surface state and low-cost scalable production, and high-speed photodetection. However, the stiffness of bulk silicon crystals limits its application in the field of flexible photodetectors, especially flexible detection electronics. However, when the Si film is thinned to less than 50 microns, the application flexibility is better, it is easy to bend, and can be cut with ordinary scissors, making it of certain application value in flexible electronic applications.

Contents of the invention

The object of the present invention is to provide a method for preparing a flexible and transparent graphene/silicon metal-semiconductor-metal (MSM) photodetector against the deficiencies of the prior art.

The object of the present invention is achieved by the following technical solutions: a method for preparing a flexible and transparent graphene/silicon metal-semiconductor-metal photodetector, comprising the following steps:

(1) The silicon film of the SOI silicon substrate is etched into a rectangular silicon strip by using a deep-level reactive etching machine ICP, and the SOI silicon substrate includes a silicon film, a silicon dioxide isolation layer and a silicon lining from top to bottom end;

(2) On the upper surface of the silicon dioxide isolation layer, a gold electrode pattern located on both sides of the silicon strip and parallel to the silicon strip is photoetched, and then the gold electrode is plated by electron beam evaporation technology;

(3) A single crystal graphene film is prepared on a copper foil substrate by chemical vapor deposition;

(4) Cover the single crystal graphene film on the surface of the silicon dioxide isolation layer, silicon strips and gold electrodes;

(5) The single crystal graphene film is patterned into an interdigitated shape using photolithography technology, and then the excess graphene is removed by plasma etching. The coverage of the patterned single crystal graphene film is within the range surrounded by the gold electrode ;

(6) The upper surface of the patterned device obtained in the step is covered with a PC film, the edge PC film is scraped off, and the silicon substrate is etched in a BOE etching solution to prepare a flexible, transparent and ultra-thin graphene/silicon metal - Semiconductor-metal photodetectors.

Further, in the step, the thickness of the silicon film is 200nm, the thickness of the silicon strip is 200nm, and the thickness of the silicon dioxide isolation layer is 100nm.

Further, in the step, first grow a chromium adhesion layer with a thickness of 5 nm on the silicon dioxide isolation layer, and then grow a 60 nm gold electrode.

Further, in the step, the transfer method of graphene is: evenly coat a layer of polymethyl methacrylate film on the surface of the single crystal graphene film, and then put it into the etching solution for 4 hours to remove the copper foil by etching, leaving Single-crystalline graphene film supported by polymethyl methacrylate; the single-crystalline graphene film supported by polymethyl methacrylate was washed with deionized water and transferred to the silica spacer, silicon strip and gold electrode surface; finally remove polymethyl methacrylate with dichloromethane and isopropanol; wherein, the etching solution is composed of CuSO4, HCl and water, CuSO4:HCl:H2O=10g:50ml:50ml.

The invention has the following beneficial effects: the detector uses graphene as the active layer and transparent electrode, eliminates the dead layer, and enhances the absorption of incident light; the silicon dioxide isolation layer reduces the influence of the silicon surface state, and at the same time suppresses reverse saturation current; it can work normally at a small bias voltage. The thickness of the patterned silicon strips used in the present invention is about 200nm, which is far less than the diffusion length (μm) of bulk silicon, which is beneficial to the separation of photogenerated carriers and can effectively Distinguish between light and dark currents and improve the performance of photodetectors; the prepared ultra-thin graphene MSM photodetectors are flexible and transparent, theoretically can be transferred to any carrier, and have good performance. At the same time, UV imaging can be performed on its array. The incident light irradiates the surface of the photodetector of the present invention and is absorbed by the graphene and the silicon substrate. The generated photo-generated carriers (hole-electron pairs) are separated under the action of the built-in electric field, and the direction of the electric field is directed from silicon to graphene. Under the reverse bias voltage, the electric field is stronger, the photogenerated holes move to the graphene, and the photogenerated electrons flow to the silicon substrate, forming a photogenerated current. In the present invention, the MSM photodetector is an interdigitated structure, and the array thereof can be used for ultraviolet imaging. The material used in the photodetector of the invention uses silicon as the basic material, the preparation process is simple, the cost is low, and it is easy to be compatible with the existing semiconductor standard process.

Description of drawings

Fig. 1 is the structural representation of flexible transparent graphene/silicon metal-semiconductor-metal photodetector of the present invention;

Fig. 2 is the optical response curve of the photodetector prepared by the embodiment of the present invention working at -2-2V, under different incident light powers, when the light is on and the light is off;

Among Fig. 3 (a) is the equipment used for ultraviolet imaging in the present invention; (b) is marked as the original picture of ZJU; (c) is the figure that presents ZJU under ultraviolet light irradiation; (d) is marked as the original picture of ISEE; ( e) The image showing ISEE under UV light irradiation.

detailed description

The operating principle of a flexible and transparent graphene/silicon metal-semiconductor-metal photodetector provided by the invention is as follows:

The incident light irradiates the surface of the photodetector of the present invention and is absorbed by the graphene and the silicon substrate. The generated photo-generated carriers (hole-electron pairs) are separated under the action of the built-in electric field, and the direction of the electric field is directed from silicon to graphene. Under the reverse bias voltage, the electric field is stronger, the photogenerated holes move to the graphene, and the photogenerated electrons flow to the silicon substrate, forming a photogenerated current. The thickness of patterned silicon strips is about 200nm, which is much smaller than the diffusion length (μm) of bulk silicon, which is conducive to the separation of photogenerated carriers, can effectively distinguish between light and dark currents, and improve the performance of photodetectors. The graphene MSM detector of the present invention can be transferred to the PC film.

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

A kind of method for preparing above-mentioned flexible transparent graphene/silicon metal-semiconductor-metal photodetector provided by the present invention comprises the following steps:

(1) The silicon thin film of the SOI silicon substrate (1) is etched into a rectangular silicon strip (3) using a deep-level reactive etching machine ICP, and the SOI silicon substrate (1) includes a silicon thin film from top to bottom , a silicon dioxide isolation layer (2) and a silicon substrate (1);

(2) On the upper surface of the silicon dioxide isolation layer (2), a gold electrode pattern located on both sides of the silicon strip (3) and parallel to the silicon strip (3) is photoetched, and then the gold electrode (4) is plated with electron beam evaporation technology ;

(3) Prepare a single crystal graphene film (5) on a copper foil substrate by chemical vapor deposition;

(4) Covering the single crystal graphene film (5) on the upper surface of the silicon dioxide isolation layer (2), the silicon strip (3) and the gold electrode (4);

(5) Pattern the single-crystal graphene film (5) into an interdigitated shape using photolithography, and then use plasma etching to remove excess graphene. The coverage of the patterned single-crystal graphene film (5) is Within the range surrounded by gold electrodes (4);

(6) The upper surface of the patterned device obtained in step (5) is covered with a PC film, the edge PC film is scraped off, and the silicon substrate (1) is etched in a BOE etching solution to prepare a flexible transparent ultra-thin film graphene/silicon metal-semiconductor-metal photodetectors.

Add a small bias voltage to the above-mentioned flexible, transparent and ultra-thin graphene/silicon metal-semiconductor-metal photodetector to make it work normally, and add different incident light powers to achieve gain, as shown in Figure 2.

The flexible and transparent graphene/silicon metal-semiconductor-metal photodetector prepared in this embodiment operates at -2-2V, and the light-dark current curve changes under the light irradiation of different incident light powers of 405nm are shown in Figure 2 Show. Wherein a small bias voltage is applied on the gold electrode 4 of the device. It can be seen from Figure 2 that the dark current of the prepared device is very small under the condition of no light; however, when the incident wavelength is 405nm and the incident light power gradually increases from 0.2 optical power to 0.4mW, an obvious photocurrent is generated. It can be seen from Figure 2 that when the device works at -2-2V, the curve is a smooth S-shaped curve, that is, the back-to-back Schottky junction characteristic curve. At the same time, it is found that the device has very superior photodetection characteristics from ultraviolet to near infrared.

Figure 3 is the ultraviolet imaging image of the array device. It can be seen that the image is very clear and the performance is excellent.

Claims (4)

1. a method for preparing flexible transparent graphene/silicon metal-semiconductor-metal photodetector, is characterized in that, comprises the following steps: (1) The silicon thin film of the SOI silicon substrate (1) is etched into a rectangular silicon strip (3) using a deep-level reactive etching machine ICP, and the SOI silicon substrate (1) includes a silicon thin film from top to bottom , a silicon dioxide isolation layer (2) and a silicon substrate (1); (2) On the upper surface of the silicon dioxide isolation layer (2), a gold electrode pattern located on both sides of the silicon strip (3) and parallel to the silicon strip (3) is photoetched, and then the gold electrode (4) is plated with electron beam evaporation technology ; (3) Prepare a single crystal graphene film (5) on a copper foil substrate by chemical vapor deposition; (4) Covering the single crystal graphene film (5) on the upper surface of the silicon dioxide isolation layer (2), the silicon strip (3) and the gold electrode (4); (5) Pattern the single-crystal graphene film (5) into an interdigitated shape using photolithography, and then use plasma etching to remove excess graphene. The coverage of the patterned single-crystal graphene film (5) is Within the range surrounded by gold electrodes (4); (6) The upper surface of the patterned device obtained in step (5) is covered with a PC film, the edge PC film is scraped off, and the silicon substrate (1) is etched in a BOE etching solution to prepare a flexible transparent ultra-thin film graphene/silicon metal-semiconductor-metal photodetectors. 2. a kind of method for preparing flexible transparent graphene/silicon metal-semiconductor-metal photodetector according to claim 1, is characterized in that, in described step (1), described silicon film thickness is 200nm, The thickness of the silicon strip (3) is 200nm, and the thickness of the silicon dioxide isolation layer (2) is 100nm. 3. a kind of method preparing flexible transparent graphene/silicon metal-semiconductor-metal photodetector according to claim 1, is characterized in that, in described step (2), at first in silicon dioxide isolation layer ( 2) A chromium adhesion layer with a thickness of 5 nm is grown on it, and then a gold electrode (4) with a thickness of 60 nm is grown. 4. a kind of method for preparing flexible transparent graphene/silicon metal-semiconductor-metal photodetector according to claim 1, is characterized in that, in described step (4), the transfer method of graphene is: The surface of the single-crystal graphene film (5) is evenly coated with a layer of polymethyl methacrylate film, and then put into an etching solution for 4 hours to etch and remove the copper foil, leaving a single-crystal graphene supported by polymethyl methacrylate Film (5); the single crystal graphene film (5) supported by polymethyl methacrylate is cleaned with deionized water and transferred to the silicon dioxide isolation layer (2), silicon strip (3) and gold electrode (4) The upper surface; finally remove polymethyl methacrylate with dichloromethane and isopropanol; wherein, the etching solution is composed of CuSO4, HCl and water, CuSO4: HCl: H2O=10g:50ml:50ml.