CN106601857B - Photoconductive detector and preparation method based on boron-doping silicon quantum dot/graphene/silicon dioxide - Google Patents

Abstract

The invention discloses a photoconductive detector based on boron-doped silicon quantum dots/graphene/silicon dioxide and a preparation method thereof. The photoconductive detector comprises a p-type silicon substrate, a silicon dioxide isolation layer, a top electrode, graphite Graphene film, boron-doped silicon quantum dot film and bottom electrode; the photoconductive detector of the present invention can carry out wide-spectrum detection, solves the problem of low response to infrared detection of traditional silicon-based PIN junctions; the detector uses graphene as the active layer and The 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; it can work normally at a small bias voltage, and the boron-doped silicon quantum dot layer absorbs light and converts it into photogenerated carriers , the generated photo-generated carriers (hole-electron pairs) are separated under the action of the built-in electric field, which can obtain ultra-high gain; the preparation process adopted in the present invention is simple, low in cost, high in responsiveness, fast in response, and internal Large gain, small switch ratio, and easy integration.

Description

Photoconductive detector based on boron-doped silicon quantum dots/graphene/silicon dioxide and its preparation method

technical field

The invention belongs to the technical field of photodetection, relates to the structure of a photodetector device, in particular to a photoconductive detector (FET) based on boron-doped silicon quantum dots/graphene/silicon dioxide and a preparation method.

Background technique

Optical detectors have a wide range of applications in chemical material analysis, medical and health care, and space technology. Photodetectors have the advantages of high sensitivity, high optical response, and fast response speed, and have important applications in high-speed modulation and weak signal monitoring. Traditional silicon-based PIN junction detectors require thermal diffusion or ion implantation processes, and have almost no absorption of infrared light, so the response in the infrared band decreases rapidly or even becomes zero as the wavelength of the incident light increases. Therefore, there is a need to improve the response of silicon photodetection devices to long-wavelength infrared light.

Graphene is a honeycomb two-dimensional planar crystal film composed of a single layer of ^sp2 hybridized carbon atoms, which has excellent mechanical, thermal, optical, electrical and other properties. Unlike ordinary metals, graphene is a new type of two-dimensional conductive material with transparency and flexibility. Single-layer graphene absorbs only 2.3% of light and can be used as a transparent conductive film. Boron-doped silicon quantum dots are prepared by cold plasma method. Boron-doped silicon quantum dots can be prepared by adding a precursor of boron atoms to the plasma. Boron-doped silicon quantum dots have absorption in the visible near-infrared and even mid-infrared, especially the mid-infrared has a strong absorption peak, there is a local plasmon effect (LSPR), the preparation process is simple, and it is widely used in the field of photoelectric detection. Since the boron-doped silicon quantum dot film is in contact with graphene, it will transfer charges to graphene, and it is also an anti-reflection film to reduce surface recombination, which can solve the dead layer problem and improve infrared optical response.

Contents of the invention

The object of the present invention is to provide a photoconductive detector based on boron-doped silicon quantum dots/graphene/silicon dioxide and a preparation method for the deficiencies of the prior art.

The purpose of the present invention is achieved by the following technical solutions: a photoconductive detector based on boron-doped silicon quantum dots/graphene/silicon dioxide, comprising: p-type silicon substrate, silicon dioxide isolation layer, top electrode , a graphene film, a boron-doped silicon quantum dot film and a bottom electrode; wherein, the upper surface of the p-type silicon substrate is covered with a silicon dioxide isolation layer, and the upper surface of the silicon dioxide isolation layer is covered with two top electrodes. The upper surface of the two top electrodes and the upper surface of the silicon dioxide isolation layer between the two top electrodes are covered with a graphene film, the upper surface of the graphene film is covered with a boron-doped silicon quantum dot film, and the bottom electrode is set on the lower surface of the p-type silicon substrate .

Further, the thickness of the silicon dioxide isolation layer is 100 nm.

Further, the top electrode is a metal thin film electrode made of aluminum, gold or gold-chromium alloy.

Further, the bottom electrode is a metal thin film electrode made of gallium indium alloy, titanium gold alloy or aluminum.

Further, the boron-doped silicon quantum dots are prepared by a cold plasma method, and boron-doped silicon quantum dots are prepared by adding a precursor of boron atoms in the plasma; the precursor of boron atoms is diborane ( B ₂ H ₆ ). Boron-doped silicon quantum dots have absorption in the visible near-infrared and even in the mid-infrared, especially the mid-infrared has a strong absorption peak, and there is a local plasmon effect (LSPR).

A preparation method based on boron-doped silicon quantum dot/graphene/silicon dioxide photoconductive detector, comprising the following steps:

(1) Oxidize and grow a silicon dioxide isolation layer on the upper surface of a p-type silicon substrate, the resistivity of the p-type silicon substrate used is <0.01Ω·cm; the thickness of the silicon dioxide isolation layer is 100nm, and the growth temperature is 900 ~1200℃;

(2) Photoetch two top electrode patterns on the surface of the silicon dioxide isolation layer, and then use electron beam evaporation technology to first grow a chromium adhesion layer with a thickness of about 5nm, and then grow a top electrode with a thickness of 60nm;

(3) Preparation of graphene film: adopt chemical vapor deposition method to prepare graphene film on copper foil substrate;

(4) Cover graphene film on the upper surface of two top electrodes and the upper surface of the silicon dioxide isolation layer between two top electrodes; wherein, the transfer method of graphene is: the surface of graphene film is uniformly coated with one layer Methyl methacrylate film, then put into the etching solution for 4h to etch and remove the copper foil, leaving a graphene film supported by polymethyl methacrylate; the graphene film supported by polymethyl methacrylate was deionized After washing with water, transfer to the upper surface of the silicon dioxide isolation layer and the top electrode; finally remove the polymethyl methacrylate with acetone and isopropanol; wherein, the etching solution is composed of CuSO ₄ , HCl and water, CuSO ₄ : HCl: H ₂ O = 10g:50ml:50ml;

(5) Spin-coat a boron-doped silicon quantum dot film on the surface of the patterned device. The boron-doped silicon quantum dot has a strong absorption peak in the visible light, especially the infrared band, with a particle size of 6nm and a rotational speed of 2000rpm for 30s. The film thickness is about 105 nm.

(6) Coating gallium indium paste on the bottom of the p-type silicon substrate to prepare a gallium indium bottom electrode to form an ohmic contact with the p-type silicon substrate.

The present invention has the following beneficial effects:

1. The incident light is irradiated on the surface of the photodetector of the present invention, and is absorbed by graphene, boron-doped silicon quantum dots and the substrate. Add a small bias voltage to both ends of the device, and the generated photocarriers (hole-electron pairs) are separated under the action of the built-in electric field. It is quickly extracted, before the minority carriers are released, it is equivalent to the charge being circulated many times in the loop, thus forming a large optical signal current with high gain.

2. Boron-doped silicon quantum dots have strong absorption peaks in visible light, especially in the infrared band, and have local plasmon effects. The incident light is easily absorbed, and the generated electron holes are quickly separated by the internal electric field, reducing surface recombination and eliminating dead layers. In the infrared region, the quantum efficiency is very high.

3. Graphene, as a transparent electrode, enhances the absorption of incident light, improves the photogenerated current, and has a high optical response. Graphene has a large carrier mobility, which can improve the time response of the device.

4. The material used in the photodetector of the present invention is 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 the photoconductive detector based on boron-doped silicon quantum dot/graphene/silicon dioxide of the present invention;

Fig. 2 is the optical response curve of the photodetector prepared in the embodiment of the present invention working at -1-1V voltage, infrared light with 532nm and light energy of 0.2μW/cm ² under light-on and light-off conditions.

Detailed ways

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

As shown in Figure 1, a kind of photoconductive detector based on boron-doped silicon quantum dot/graphene/silicon dioxide provided by the present invention includes: p-type silicon substrate 1, silicon dioxide isolation layer 2, top electrode 3 , a graphene film 4, a boron-doped silicon quantum dot film 5 and a bottom electrode 6; wherein, the upper surface of the p-type silicon substrate 1 is covered with a silicon dioxide isolation layer 2, and the upper surface of the silicon dioxide isolation layer 2 is covered Two top electrodes 3, the upper surface of the two top electrodes 3 and the upper surface of the silicon dioxide isolation layer 2 between the two top electrodes 3 are covered with a graphene film 4, and the upper surface of the graphene film 4 is covered with boron-doped silicon quantum dots The thin film 5 is provided with a bottom electrode 6 on the lower surface of the p-type silicon substrate 1 .

Further, the silicon dioxide isolation layer 2 has a thickness of 100 nm.

Further, the top electrode 3 is a metal thin film electrode made of aluminum, gold or gold-chromium alloy.

Further, the bottom electrode 6 is a metal film electrode made of gallium-indium alloy, titanium-gold alloy or aluminum.

Further, the boron-doped silicon quantum dot 5 is prepared by a cold plasma method, by adding a boron atom precursor to the plasma to prepare a boron-doped silicon quantum dot; the boron atom precursor is diborane (B ₂ H ₆ ). Boron-doped silicon quantum dots have absorption in the visible near-infrared and even in the mid-infrared, especially the mid-infrared has a strong absorption peak, and there is a local plasmon effect (LSPR).

The working principle of the photoconductive detector based on boron-doped silicon quantum dot/graphene/silicon dioxide in the present invention is as follows:

The incident light is irradiated on the surface of the photodetector of the present invention, and is absorbed by the graphene, the boron-doped silicon quantum dots and the substrate. Add a small bias voltage to both ends of the device, and the generated photocarriers (hole-electron pairs) are separated under the action of the built-in electric field. It is quickly extracted, before the minority carriers are released, it is equivalent to the charge being circulated many times in the loop, thus forming a large optical signal current with high gain.

Boron-doped silicon quantum dots have strong absorption peaks in visible light, especially in the infrared band, and the incident light is easily absorbed, and the generated electron holes are quickly separated by the internal electric field, reducing surface recombination and eliminating dead layers. In the infrared region, the quantum efficiency is very high.

The method for preparing the above-mentioned photoconductive detector based on boron-doped silicon quantum dots/graphene/silicon dioxide comprises the following steps:

(1) Oxidize and grow a silicon dioxide isolation layer (2) on the upper surface of the p-type silicon substrate (1), the resistivity of the p-type silicon substrate (1) used is <0.01Ω·cm; the silicon dioxide isolation layer (2) The thickness is 100nm, and the growth temperature is 900-1200°C;

(2) Photoetch two top electrode (3) patterns on the surface of the silicon dioxide isolation layer (2), and then use electron beam evaporation technology to first grow a chromium adhesion layer with a thickness of about 5 nm, and then grow a gold layer with a thickness of 60 nm. electrode;

(3) Preparation of graphene film (4): using chemical vapor deposition method to prepare graphene film (4) on copper foil substrate;

(4) cover the graphene film (4) on the silicon dioxide isolation layer (2) upper surface between two top electrodes (3) upper surfaces and two top electrodes (3); wherein, the transfer method of graphene is : the surface of the graphene film (4) is evenly coated with a layer of polymethyl methacrylate (PMMA) film, then put into an etching solution for 4h to remove the copper foil by corrosion, leaving graphite supported by polymethyl methacrylate Graphene film (4); After the graphene film (4) supported by polymethyl methacrylate is cleaned with deionized water, it is transferred to the upper surface of the silicon dioxide spacer (2) and the top electrode (3); and isopropanol to remove polymethyl methacrylate; wherein, the etching solution is composed of CuSO ₄ , HCl and water, CuSO ₄ : HCl: H ₂ O=10g:50ml:50ml;

(5) Spin-coat a layer of boron-doped silicon quantum dot film (5) on the surface of the patterned device. The boron-doped silicon quantum dot has a strong absorption peak in visible light, especially in the infrared band, with a particle size of 6nm and a rotational speed of 2000rpm for 30s.

(6) Coating gallium indium paste on the bottom of the p-type silicon substrate (1), preparing a gallium indium bottom electrode (6), and forming an ohmic contact with the p-type silicon substrate (1).

Add a small bias voltage to the photoconductive detector based on boron-doped silicon quantum dots/graphene/silicon dioxide to make it work normally, and add different lighting conditions to achieve gain. As shown in Figure 1.

The photoconductive detector based on boron-doped silicon quantum dots/graphene/silicon dioxide prepared in this example works at a voltage of -1V-1V, and the photocurrent and gain vary with wavelength under the irradiation of light of different wavelengths and powers as shown in picture 2. Wherein, a small bias voltage is applied to the top electrode 3 of the device, and a voltage of -50V-50V is applied to the bottom electrode 6 of the device to modulate the graphene energy band, as shown in FIG. 1 . It can be seen from Figure 2 that the photocurrent and response of the non-spin-coated borosilicate quantum dots of the prepared device are very small under the condition of no light; and when the incident wavelength is 532nm, the light energy is 0.2μW/cm2 when the laser is irradiated produce a significant photocurrent. When the device works at 1V, in the full spectral range (300-1900nm), the optical response is 10^9, and the gain is 10^12, which proves that the device has very superior photodetection characteristics, especially in the infrared band.

Claims (2)

1. A method for preparing a photoconductive detector based on boron-doped silicon quantum dot/graphene/silicon dioxide, characterized in that, the photoconductive detector based on boron-doped silicon quantum dot/graphene/silicon dioxide Including: p-type silicon substrate (1), silicon dioxide isolation layer (2), top electrode (3), graphene film (4), boron-doped silicon quantum dot film (5) and bottom electrode (6); , the upper surface of the p-type silicon substrate (1) is covered with a silicon dioxide isolation layer (2), the upper surface of the silicon dioxide isolation layer (2) is covered with two top electrodes (3), and the two top electrodes (3) The upper surface of the upper surface and the silicon dioxide isolation layer (2) between the two top electrodes (3) is covered with a graphene film (4), and the upper surface of the graphene film (4) is covered with a boron-doped silicon quantum dot film (5), a bottom electrode (6) is arranged on the lower surface of the p-type silicon substrate (1); the preparation method comprises the following steps: (1) Oxidize and grow a silicon dioxide isolation layer (2) on the upper surface of the p-type silicon substrate (1), the resistivity of the p-type silicon substrate (1) used is <0.01Ω·cm; the silicon dioxide isolation layer (2) The thickness is 100nm, and the growth temperature is 900-1200°C; (2) Photoetch two top electrode (3) patterns on the surface of the silicon dioxide isolation layer (2), and then use electron beam evaporation technology to first grow a chromium adhesion layer with a thickness of about 5 nm, and then grow a top electrode (3) with a thickness of 60 nm. electrode (3); (3) Preparation of the graphene film (4): the graphene film (4) is prepared on the copper foil substrate by chemical vapor deposition; (4) cover the graphene film (4) on the silicon dioxide isolation layer (2) upper surface between two top electrodes (3) upper surfaces and two top electrodes (3); wherein, the transfer method of graphene is : Graphene film (4) surface is evenly coated with one deck polymethyl methacrylate film, puts into etching solution 4h to corrode and removes copper foil then, stays the graphene film supported by polymethyl methacrylate ( 4); After the graphene film (4) supported by polymethyl methacrylate is cleaned with deionized water, it is transferred to the upper surface of the silicon dioxide isolation layer (2) and the top electrode (3); finally use acetone and isopropyl Alcohol removal of polymethyl methacrylate; wherein, the etching solution is composed of CuSO ₄ , HCl and water, CuSO ₄ : HCl: H ₂ O = 10g:50ml:50ml; (5) Spin-coat a layer of boron-doped silicon quantum dot film on the surface of the patterned device (5), boron-doped silicon quantum dots have absorption in visible light and infrared bands, and have obvious absorption peaks in the infrared band, with a particle size of 6nm , the speed is 2000rpm, 30s; the film thickness is 105nm; (6) Coating gallium indium paste on the bottom of the p-type silicon substrate (1), preparing a gallium indium bottom electrode (6), and forming an ohmic contact with the p-type silicon substrate (1). 2. method according to claim 1, is characterized in that, described boron-doped silicon quantum dot (5) is prepared by cold plasma method, prepares boron-doped by adding the precursor of boron atom in plasma Silicon quantum dots; the precursor of boron atoms is diborane (B ₂ H ₆ ); boron-doped silicon quantum dots have absorption in visible light, near-infrared and mid-infrared, and have obvious absorption peaks in mid-infrared, and there are local plasmons Laminar effect (LSPR).