A silicon-based infrared band avalanche photodetector and a method for preparing the same

Abstract

The present invention discloses a silicon-based infrared band avalanche photodetector and a preparation method thereof, comprising a bottom electrode layer, a silicon film layer and a top metal film layer stacked in sequence, wherein the bottom electrode layer forms an ohmic contact with the silicon film layer, and the top metal film layer forms a Schottky contact with the silicon film layer; the photodetector absorbs near-infrared light through the top metal film layer, generates hot carriers and injects them into the silicon film layer, which are then collected by the bottom electrode layer to form a photocurrent, thereby realizing the detection of infrared light below the energy band gap of silicon; and by adjusting the thickness of the silicon film layer and the type of the top metal film layer, broadband or narrowband optical high absorption at different infrared wavelengths can be achieved. In addition, when a bias voltage of less than 3V is applied to the photodetector, photoconductivity gain and avalanche effect can be generated, and the photoelectric responsivity is increased by 3-4 orders of magnitude, and the responsivity in the 1200-2000nm band reaches 0.1-0.35A / W, which is comparable to the performance of commercial germanium and indium gallium arsenide infrared photodetectors.

Description

Technical Field

[0001] The present invention relates to the field of photoelectric detection technology, and in particular to a silicon-based infrared band avalanche photoelectric detector and a preparation method thereof. Background Art

[0002] Silicon-based photodetectors are widely used in communications, sensing, industrial detection, and medical fields due to their mature complementary metal oxide semiconductor (CMOS) manufacturing process, room temperature operation, and low production cost. As optoelectronic devices develop towards miniaturization and integration, the development of monolithic integrated silicon-based photodetectors for infrared wavelengths based on mature CMOS technology is an important step in the development of silicon photonics technology. Although silicon-based photodetectors have been widely used in the visible spectrum range (0.4-0.7μm), they are not suitable for detecting near-infrared light with wavelengths greater than 1.1μm. This is because the energy of these near-infrared photons is not enough to overcome the silicon band gap (1.12eV) and induce the photogeneration of electron-hole pairs, that is, no photocurrent is generated. In order to address the problem that silicon does not absorb infrared light, a solution proposed by the silicon photonics industry is to combine low-bandgap germanium (0.67eV) with silicon, or to integrate III-V, II-VI, and VI-VI compound semiconductors on silicon wafers using wafer bonding technology. Therefore, commercial infrared photodetectors mostly use materials based on germanium, indium antimonide, indium gallium arsenide and mercury cadmium telluride. Although they can achieve light detection in the infrared band, the devices require complex preparation processes, and the III-V, II-VI, and VI-VI materials used are incompatible with silicon-based CMOS digital readout circuits, and the materials and devices have poor stability.

[0003] In order to overcome the above problems, hot electron photodetection technology is used. Metal materials absorb light to generate hot carriers, which are then injected into semiconductors to generate photocurrent. Since the Schottky energy barrier is lower than the semiconductor band width, hot electron detection technology can be used to expand the photodetection band. This type of hot electron device has the advantages of self-driving at room temperature, compatibility with silicon-based processes, adjustable working wavelength, detection bandwidth, and polarization sensitivity. However, due to various energy losses in hot electron photodetection, the device efficiency is always less than 1%, which is difficult to reach commercial levels, thus limiting the practical application of such hot electron devices. Therefore, how to effectively improve the responsiveness of photodetectors while expanding the photodetection band is the key to promoting the commercialization of hot electron photodetectors.

[0004] To improve the responsivity of this type of hot electron photodetector, Cheng Zhang et al. designed a gold-wrapped silicon nanocone structure [Adv. Funct. Mater. 2023, 2304368]. The hybrid plasma mode along the cone tip provides huge field enhancement and broadband response. Ilya Goykhman et al. reported an on-chip integrated metal graphene-silicon plasma Schottky photodetector [Nano Lett. 2016, 16, 3005-3013], which achieved avalanche multiplication under a reverse bias of 3V and a responsivity of 0.37A / W. Although this type of photodetector has improved the responsivity to a certain extent, the unique nanostructure has high processing requirements and is not suitable for actual production. In addition, the detection band is limited and rarely detects the infrared band.

[0005] Based on this, there is an urgent need for a silicon-based room-temperature infrared photodetector with a simple structure that can detect near-infrared light with a wavelength greater than 1.1μm and whose performance is comparable to that of commercial germanium and indium gallium arsenide infrared photodetectors. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a silicon-based infrared band avalanche photodetector and a preparation method thereof. The photodetector has a simple structure and consists of a bottom electrode layer, a silicon film layer and a top metal film layer. It can detect near-infrared light in the 1200-2000nm band, and can excite a strong electric field in the silicon film to induce photoconductivity gain and avalanche effect under the application of a small bias voltage, so that the device response is equivalent to that of commercial infrared photodetectors such as germanium and indium gallium arsenide; in addition, by selecting the material of the top metal film layer, the photodetector can form a planar Fabry-Perot cavity structure to achieve narrow-band light detection. Under the condition of applying a small bias voltage, a strong electric field can be excited in the silicon film to induce photoconductivity gain and avalanche effect, thereby improving the light response of the device by 3-4 orders of magnitude, and the narrow-band peak wavelength can be adjusted by regulating the thickness of the silicon film layer.

[0007] The present invention provides the following technical solutions:

[0008] A first aspect of the present invention provides a silicon-based infrared band avalanche photodetector, the photodetector comprising a bottom electrode layer, a silicon film layer and a top metal film layer stacked in sequence;

[0009] The top metal film layer forms a Schottky contact with the silicon film layer;

[0010] The silicon film layer has a thickness of 10 nm-5 μm.

[0011] The silicon-based infrared band avalanche photodetector provided by the present invention consists only of a bottom electrode layer, a silicon film layer and a top metal film layer, wherein the top metal film layer absorbs near-infrared light, the transition metal layer and silicon form a Schottky junction, and the photoexcited hot carriers generated by the top metal film layer after being irradiated by light cross the Schottky barrier and are injected into the silicon film layer, and then are collected by the bottom electrode layer to form a photocurrent, thereby realizing the detection of infrared light below the energy band gap of silicon.

[0012] Furthermore, the bottom electrode layer forms an ohmic contact with the silicon film layer, which is beneficial to the collection of photogenerated carriers; at the same time, the bottom electrode layer acts as an optical reflector to improve the light absorption efficiency of the top metal film layer.

[0013] Furthermore, the material of the bottom electrode layer is one or more of aluminum, noble metals and transition metals, preferably one or more of titanium, gold, silver, copper, chromium and aluminum.

[0014] Furthermore, the thickness of the bottom electrode layer is preferably greater than 30 nm, such as 50-200 nm.

[0015] Furthermore, the bottom electrode layer is obtained by stacking a titanium film layer, a gold film layer and an aluminum film layer in sequence, and the aluminum film layer is bonded to the silicon film layer; more preferably, the thickness of the titanium film layer is greater than 2nm, the thickness of the gold film layer is greater than 40nm, and the thickness of the aluminum film layer is greater than 30nm. The bottom electrode layer obtained by stacking the above three metal films, and the aluminum film layer is bonded to the silicon film layer, on the one hand, reduces the contact barrier between the bottom electrode layer and the silicon film layer, and at the same time, the stacked titanium film layer and the gold film layer can improve the reflection of the bottom electrode layer to light, thereby improving the light absorption efficiency of the top metal film layer.

[0016] Furthermore, the material of the silicon film layer is a lightly doped n-type crystalline silicon material or a lightly doped p-type crystalline silicon material; when the silicon film layer is a lightly doped n-type or p-type silicon film, the silicon film layer forms an ohmic contact with the aluminum film layer; more preferably, the resistivity of the silicon film layer is preferably 0.1-100Ω·cm.

[0017] Further, the thickness of the silicon film layer can be any value within the range of 10-100nm, 100-200nm, 200-300nm, 300-400nm, 400-500nm, 500nm-1μm, 1-2μm, 2-3μm, 3-4μm, 4-5μm, and more preferably 10nm-1μm. The silicon film layer of the silicon-based photodetector protected by the present invention is much smaller than the thickness of the silicon substrate in the existing silicon-based photodetector (several hundred microns). More preferably, the thickness of the silicon film layer is smaller than the depletion layer width of the Schottky junction formed by the silicon film layer and the top metal film layer, which is beneficial to the collection of carriers by the bottom electrode layer.

[0018] Further, the material of the top metal film layer is selected from one or more of gold, silver, titanium, copper, chromium, aluminum, titanium nitride and alloys containing at least two of the above metal elements, which is used to absorb near-infrared light and form a Schottky contact with the silicon film layer, and can inject the photoexcited hot carriers generated after being irradiated with light into the silicon film layer across the Schottky barrier; preferably, the thickness of the top metal film layer is 5-100nm, such as 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, etc., including but not limited to the thickness values ​​listed above, and can also be other thickness values ​​within the above range. More preferably, the thickness of the top metal film layer is less than the mean free path of electrons, so that most of the infrared light can be absorbed.

[0019] Furthermore, the photodetector can reach a responsivity of 0.1-0.35A / W to the near-infrared band of 1200-2000nm under an applied bias voltage of 1-10V, preferably below 5V (the bias voltage is generally below 5V). When a bias voltage is applied, a high-intensity electric field can be formed in the silicon film between the upper and lower metal film layers, and the carriers gain energy in the electric field to accelerate the generation of photoconductivity gain and avalanche multiplication effect, thereby increasing the photocurrent by 3-4 orders of magnitude and improving the photoelectric responsivity. However, the bias voltage that the photodetector can withstand is related to the thickness of the silicon film. The thicker the silicon film, the greater the bias voltage that can be tolerated. When the thickness of the silicon film is small, applying too much bias voltage will cause the device to break down and fail to work. The bias voltage applied to the photodetector with a silicon film layer thickness of 10nm-5μm is preferably 1-10V, and more preferably below 5V.

[0020] Furthermore, when the material of the top metal film layer is one or more of titanium, chromium, and titanium nitride, for example titanium, broadband absorption of the 1200-2000nm near-infrared band can be achieved, and the responsivity of the photodetector in the 1200-2000nm band reaches 0.1-0.35A / W, which is comparable to the performance of commercial infrared photodetectors based on germanium and indium gallium arsenide materials.

[0021] Furthermore, when the material of the top metal film layer is one or more of gold, silver, copper, aluminum and alloys containing at least two of the above metal elements, the top metal film layer and the bottom electrode layer form a Fabry-Perot cavity, and the silicon film layer is a dielectric layer in the Fabry-Perot cavity, and narrow-band optical absorption at different infrared wavelengths is achieved by adjusting the thickness of the silicon film layer. Preferably, when the top metal film layer is gold, an adhesion layer is provided between the top metal film layer and the silicon film layer, and the material of the adhesion layer is preferably one or more of titanium, chromium, aluminum and silver, so as to improve the adhesion between the top metal film layer and the silicon film layer.

[0022] Narrowband silicon-based optoelectronic devices have been widely used in various fields because they can selectively respond to light of a specific wavelength and not respond to light of other wavelengths. However, narrowband photodetectors are currently mainly integrated with inorganic semiconductors and filters, which are complex and limit the image density of the detector array; and filter-free narrowband photodetectors constructed by using materials with narrowband absorption, using plasma effects to enhance absorption in a selected wavelength range, or controlling internal quantum efficiency through charge collection and narrowing have problems such as low sensitivity and complex micro-nanostructure processing technology.

[0023] The silicon-based photodetector provided by the present invention has a simple structure, and by selecting the material of the top metal film layer, the top metal film layer and the bottom electrode layer can form a Fabry-Perot cavity, so that optical resonance can be achieved to enhance the optical absorption efficiency of the top metal film layer without the need for micro-nano structures, and the absorption peak wavelength can be controlled by regulating the thickness of the silicon film of the dielectric layer to achieve narrow-band light absorption in the infrared band. Moreover, the photodetector can effectively improve the responsiveness of the device under the application of bias voltage while maintaining the narrow-band characteristics.

[0024] The second aspect of the present invention provides a method for preparing the silicon-based infrared band avalanche photodetector according to the first aspect, comprising the following steps:

[0025] placing the pretreated silicon substrate on the insulating layer in a hydrofluoric acid solution to remove the insulating layer to obtain the silicon film layer;

[0026] A top metal film layer and a bottom electrode layer are prepared on the upper and lower surfaces of the silicon film layer respectively by physical and / or chemical methods.

[0027] Furthermore, the pretreatment includes a process of ultrasonically cleaning the silicon on the insulating layer with an organic solvent and water in sequence; the physical and / or chemical method includes magnetron sputtering deposition and electron beam evaporation.

[0028] The present invention places the silicon on the insulating layer in a hydrofluoric acid solution and uses the hydrofluoric acid to dissolve the insulating layer (such as silicon dioxide), thereby obtaining an ultra-thin silicon film on the surface of the silicon on the insulating layer.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The present invention provides a silicon-based infrared band avalanche photodetector, which is composed of only a bottom electrode layer, an ultra-thin silicon film layer and a top metal film layer. It has a simple structure and is easy to prepare, suitable for mass production. It is light and thin, meeting the needs of device miniaturization. Moreover, by selecting the material of the top metal film layer, broadband absorption or narrowband absorption of the near-infrared band can be achieved, thereby meeting different application requirements.

[0031] 2. The silicon-based infrared band avalanche photodetector provided by the present invention has a planar multilayer structure and is insensitive to polarization and incident angle. When used as a broadband absorption device, the allowable thickness error of the multilayer thin film structure is large. When the bottom electrode layer, the ultra-thin silicon film layer and the top metal film layer form a Fabry-Perot cavity, narrow-band light absorption can be achieved in the infrared band, and the narrow-band center wavelength can be controlled by adjusting the thickness of the silicon film, which can be used as a narrow-band absorption device.

[0032] 3. When a bias is applied to both ends of the above-mentioned photodetector, a strong electric field will be generated in the silicon film layer located between the upper and lower metal film layers. The carriers gain energy in the electric field and accelerate to produce photoconductivity gain and avalanche multiplication effect, thereby increasing the photocurrent by 3-4 orders of magnitude, greatly improving the device's response to near-infrared light wavelengths; and when used as a narrow-band absorption device, applying a bias can improve the device's response, while the half-width remains basically unchanged, and the narrow-band characteristics can still be maintained. For example, a broadband photodetector prepared by the present invention can make the device's photoresponsivity at 1600-1800nm ​​close to 0.3A / W under a bias of -2V, which is more than 3 orders of magnitude higher than the photoresponsivity at zero bias. In addition, a narrow-band photodetector prepared by the present invention can make the device's photoresponsivity at 1550nm reach 0.2A / W under a bias of 1.9V, and the narrow-band peak absorption wavelength can be adjusted to 1780nm by adjusting the thickness of the silicon film layer of the device. The device's responsivity reaches 0.12A / W under a bias of 3V, which is more than 3 orders of magnitude higher than the photoresponsivity at zero bias, and is comparable to the performance of commercial infrared photodetectors based on germanium and indium gallium arsenide materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the structure of a silicon-based infrared band avalanche photodetector prepared in Example 1, wherein 1 is a bottom electrode layer, 2 is a silicon film layer, and 3 is a top metal film layer;

[0034] Figure 2 Flow chart of preparing a silicon-based infrared band avalanche photodetector for Example 1;

[0035] Figure 3 middle: Figure 3 a is the absorption / reflection spectrum of the silicon-based infrared band avalanche photodetector prepared in Example 1, where the solid line is the absorptivity curve and the dotted line is the reflectivity curve; Figure 3 b is the dark state current-voltage curve of the photodetector;

[0036] Figure 4 middle: Figure 4 a is the photocurrent time curve of the silicon-based infrared band avalanche photodetector prepared in Example 1 under laser irradiation of different wavelengths at zero bias; Figure 4b is the responsivity curve of the silicon-based infrared band avalanche photodetector prepared in Example 1 to the 1200nm-2000nm band under zero bias;

[0037] Figure 5 The photocurrent-time curves of the silicon-based infrared band avalanche photodetector prepared in Example 1 at different wavelengths under different bias voltages are shown in FIG. Figure 5 a: -1V bias, Figure 5 b: -2V bias;

[0038] Figure 6 middle: Figure 6 a is the responsivity curve of the silicon-based infrared band avalanche photodetector prepared in Example 1 at different bias voltages (-0.5V, -1V, -1.5V, -2V); Figure 6 b is the photocurrent gain curve of the silicon-based infrared band avalanche photodetector prepared in Example 1 at different bias voltages, taking the wavelength of 1600nm as an example;

[0039] Figure 7 This is a schematic diagram of the structure of a silicon-based infrared band avalanche photodetector prepared in Example 2, wherein 1 is a bottom electrode layer, 2 is a silicon film layer, 3 is an adhesion layer, and 4 is a top metal film layer;

[0040] Figure 8 Flow chart of preparing a silicon-based infrared band avalanche photodetector for Example 2;

[0041] Fig. 9 This is the absorption / reflection spectrum of the silicon-based infrared band avalanche photodetector prepared in Example 2, where the solid line is the reflectivity curve and the dotted line is the absorptivity curve;

[0042] Fig.10 The dark state current-voltage curve of the silicon-based infrared band avalanche photodetector prepared in Example 2;

[0043] Fig.11 The responsivity curve of the silicon-based infrared band avalanche photodetector prepared in Example 2 to different wavelengths under zero bias;

[0044] Fig.12 The responsivity curve of the silicon-based infrared band avalanche photodetector prepared in Example 2 to different wavelengths under a bias voltage of 1.9V;

[0045] Fig.13 This is the absorption / reflection spectrum of the silicon-based infrared band avalanche photodetector prepared in Example 3, where the solid line is the reflectivity curve and the dotted line is the absorptivity curve;

[0046] Fig.14 The responsivity curve of the silicon-based infrared band avalanche photodetector prepared in Example 3 to different wavelengths under zero bias;

[0047] Fig.15 This is the response curve of the silicon-based infrared band avalanche photodetector prepared in Example 3 to different wavelengths under a bias voltage of 3V. DETAILED DESCRIPTION

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items. The term "includes" or "comprising" described in the present invention means that it may include or contain other components in addition to the components described. The term "includes" or "comprising" described in the present invention may also be replaced by the closed form "for" or "consisting of..."

[0049] The present invention is further described below in conjunction with embodiments and drawings so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0050] Example 1

[0051] This embodiment relates to the preparation of a broadband absorption silicon-based infrared band avalanche photodetector, the structure of which is as follows Figure 1 As shown, from bottom to top, it includes:

[0052] Bottom electrode layer 1: a 5 nm thick titanium film layer, a 70 nm thick gold film layer, and a 70 nm thick aluminum film layer are stacked in sequence from bottom to top;

[0053] Silicon film layer 2: 100 nm thick;

[0054] Top metal film layer 3: 20 nm thick titanium film layer.

[0055] A polished silicon oxide wafer with a top silicon oxide layer of 300 nm thickness is used as a substrate to support the photodetector.

[0056] The preparation process of the above-mentioned photodetector is as follows Figure 2 As shown, the details are as follows:

[0057] (1) A commercial silicon-on-insulator (SOI) substrate that has been ultrasonically cleaned with acetone, ethanol, and deionized water is placed in a 40% by volume hydrofluoric acid solution to remove the silicon oxide layer, thereby obtaining a silicon film suspended in the solution.

[0058] (2) The ultra-thin silicon film prepared in step (1) was transferred to the surface of the substrate coated with PMMA and air-dried; then a 70 nm thick aluminum film layer was deposited on the surface of the ultra-thin silicon film using magnetron sputtering technology (pre-sputtering was performed for 5 min before film deposition, and the deposition vacuum was 5×10 -4 Pa, the parameters of magnetron sputtering include: the target material is aluminum target, the power is 50W, argon gas is introduced during sputtering, and the pressure in the chamber is 1Pa. ).

[0059] (3) Then the film was transferred to acetone and allowed to stand to obtain a composite film 1 suspended in an organic solvent, which was transferred to a titanium electrode and air-dried to obtain a composite film 2 comprising a bottom electrode layer-silicon film layer; wherein the titanium electrode was prepared on a substrate by electron beam evaporation (pre-sputtering for 5 min before film deposition, and the parameters of electron beam evaporation included: the evaporation material was titanium particles, the evaporation rate was 0.5 A / s, the pre-evaporation power was 30%, the evaporation power was 30%, and the working vacuum was 5e -4 Pa, the operating temperature is 20 degrees. ).

[0060] (4) A layer of photoresist is applied on the silicon film layer of the composite film 2, and a window smaller than the silicon film is exposed by a UV exposure system. Then, a 20 nm thick titanium metal film layer is deposited by electron beam evaporation technology (pre-sputtering is performed for 5 min before film deposition. The parameters of electron beam evaporation include: the evaporation material is titanium gold particles, the evaporation rate is 0.5 A / s, and the working vacuum is 5e -4 Pa, the working temperature is 20 degrees. ), then the device is immersed in acetone solution, taken out and air-dried after standing for a period of time, and a silicon-based photodetector is prepared.

[0061] In the photoelectric detector prepared by the above preparation method, the thickness of each metal film layer can be controlled by controlling various parameters in the deposition process, thereby ensuring the uniformity of the thickness of the metal film layer.

[0062] Performance Testing:

[0063] The optical and electrical properties of the silicon-based photodetector prepared in this embodiment were tested as follows:

[0064] (1) Use a spectrometer to test the optical absorption and reflectivity of the photodetector

[0065] Test results such as Figure 3 As shown in a, the average absorption rate of the silicon-based photodetector prepared in this embodiment exceeds 50% in the near-infrared band of 1200-2000nm. It can be seen that the silicon-based photodetector can achieve broadband absorption in this band.

[0066] (2) Testing the electrical response of photodetectors using a micro-area test platform

[0067] Figure 3 b is the current-voltage curve of the photodetector between -2V and 2V. It can be seen from the figure that the top metal film and the silicon film form a Schottky junction, and the silicon film and the aluminum film in the bottom electrode layer are in ohmic contact.

[0068] (3) Study the effect of bias voltage on the responsivity of photodetectors

[0069] Figure 4 a is the photocurrent curve of the photodetector under zero bias voltage when the near-infrared light of different wavelengths is turned on and off over time. The wavelength range is from 1100nm to 2000nm, with an interval of 100nm. It can be seen from the figure that the photodetector has an electrical light response to the near-infrared light of 1100nm to 2000nm; and by measuring the photocurrent of the photodetector with a smaller wavelength interval and the corresponding optical power of the laser light, the following is obtained: Figure 4 The responsivity curve of the photodetector in the near-infrared band of 1200nm to 2000nm shown in b further illustrates that the photodetector prepared in this embodiment achieves broadband absorption in the band of 1200nm to 2000nm.

[0070] Figure 5 The photocurrent time curve of the photodetector under different bias voltages and laser irradiation of different wavelengths, the wavelength range is from 1100nm to 2000nm, with an interval of 100nm. Figure 5 a is the photocurrent-time curve under -1V bias. It can be seen from the figure that the photocurrent at 1600nm is 150μA, which is 154 times the gain compared to the 1μA photocurrent at 1600nm under 0V bias. Figure 5 b is the photocurrent-time curve under -2V bias. It can be seen from the figure that the photocurrent at 1600nm is 1.492mA, which has a gain of 1492 times compared to the 1600nm photocurrent of 1μA under 0V bias, and the dark current of the sample is relatively stable under high gain.

[0071] Figure 6 a is the light responsivity curve of the photodetector to different wavelengths of light under different bias voltages. As can be seen from the figure, with the increase of bias voltage, the light responsivity also increases significantly. When the bias voltage increases to -2V, the responsivity to near-infrared light of 1600-1800nm ​​is close to 0.3A / W. Figure 6 b (The gain of the photocurrent at a wavelength of 1600nm under different bias voltages relative to that under zero bias voltage) It can be seen that with the increase of bias voltage, the gain of the photocurrent also increases, and the highest gain multiple can reach 3-4 orders of magnitude.

[0072] Example 2

[0073] This embodiment relates to the preparation of a silicon-based infrared band avalanche photodetector with narrow-band absorption, the structure of which is as follows: Figure 7As shown, from bottom to top, it includes:

[0074] Bottom electrode layer 1: a 5 nm thick titanium film layer, a 70 nm thick gold film layer, and a 70 nm thick aluminum film layer are stacked in sequence from bottom to top;

[0075] Silicon film layer 2: 100 nm thick;

[0076] Adhesion layer 3: 5 nm thick titanium film layer;

[0077] Top metal film layer 4: 14nm gold film layer.

[0078] A polished silicon oxide wafer with a top silicon oxide layer of 300 nm thickness is used as a substrate to support the photodetector.

[0079] The preparation process of the above-mentioned photodetector is as follows Figure 8 As shown, the details are as follows:

[0080] (1) A commercial silicon-on-insulator (SOI) substrate that has been ultrasonically cleaned with acetone, ethanol, and deionized water is placed in a 40% by volume hydrofluoric acid solution to remove the silicon oxide layer, thereby obtaining a silicon film suspended in the solution.

[0081] (2) The ultra-thin silicon film prepared in step (1) was transferred to the surface of the substrate coated with PMMA and air-dried; then a 70 nm thick aluminum film layer was deposited on the surface of the ultra-thin silicon film using magnetron sputtering technology (pre-sputtering was performed for 5 min before film deposition, and the deposition vacuum was 5×10 -4 Pa, the parameters of magnetron sputtering include: the target material is aluminum target, the power is 50W, argon gas is introduced during sputtering, and the pressure in the chamber is 1Pa. ).

[0082] (3) Then the film was transferred to acetone and allowed to stand to obtain a composite film 1 suspended in an organic solvent, which was transferred to a titanium electrode and air-dried to obtain a composite film 2 comprising a bottom electrode layer-silicon film layer; wherein the titanium electrode was prepared on a substrate by electron beam evaporation (pre-sputtering for 5 min before film deposition, and the parameters of electron beam evaporation included: the evaporation material was titanium particles, the evaporation rate was 0.5 A / s, the pre-evaporation power was 30%, the evaporation power was 30%, and the working vacuum was 5e -4 Pa, the operating temperature is 20 degrees. ).

[0083] (4) A layer of photoresist is applied on the silicon film layer of the composite film 2, and a window smaller than the silicon film is exposed by a UV exposure system. Then, a 5 nm thick titanium film layer and a 14 nm thick gold film layer are deposited by electron beam evaporation technology (pre-sputtering for 5 min before film deposition. The parameters of electron beam evaporation include: evaporation material is titanium or gold particles, evaporation rate is 0.5 A / s, pre-evaporation power is 30%, evaporation power is 30%, and working vacuum is 5e-4 Pa, the working temperature is 20 degrees. ), then the device is immersed in acetone solution, taken out and air-dried after standing for a period of time, and a silicon-based photodetector is prepared.

[0084] In the photoelectric detector prepared by the above preparation method, the thickness of each metal film layer can be controlled by controlling various parameters in the deposition process, thereby ensuring the uniformity of the thickness of the metal film layer.

[0085] Performance Testing:

[0086] The optical and electrical properties of the silicon-based photodetector prepared in this embodiment were tested as follows:

[0087] (1) Use a spectrometer to test the optical absorption and reflectivity of the photodetector

[0088] Test results such as Fig. 9 As shown, the reflectivity of the silicon-based photodetector prepared in this embodiment at 1550 in the near-infrared band is only 20%, the absorption rate can reach 80%, and the half-width of the absorption wavelength is 200nm. It can be seen that the silicon-based photodetector can achieve narrow-band absorption in this band.

[0089] (2) Testing the electrical response of photodetectors using a micro-area test platform

[0090] Fig.10 This is the current-voltage curve of the photodetector between -1V and 1V. It can be seen from the figure that the top metal film and the silicon film form a Schottky junction, and the silicon film and the aluminum film in the bottom electrode layer are in ohmic contact.

[0091] (3) Study the effect of bias voltage on the responsivity of photodetectors

[0092] Fig.11 The responsivity curve of the photodetector in the near-infrared band of 1200nm to 2000nm under zero bias is a narrow-band response curve that is consistent with the trend of the optical reflectance spectrum, further indicating that the photodetector can achieve narrow-band absorption at a wavelength of 1550nm.

[0093] Fig.12 This is the responsivity curve of the photodetector in the near-infrared band of 1200nm to 2000nm under a bias of 1.9V. The wavelength of the highest response is still at 1550nm, and the half-width of the narrow-band response remains at 200nm, indicating that applying a bias will not change the narrow-band absorption characteristics of the photodetector; in addition, under a bias of 1.9V, the responsivity of the photodetector at 1550nm reaches 0.2A / W, and the responsivity gain factor is 3 orders of magnitude compared to that under a bias of 0V, which is comparable to the performance of commercial detectors based on germanium and indium gallium arsenide materials.

[0094] Example 3

[0095] This embodiment relates to a silicon-based infrared band avalanche photodetector with narrow-band absorption, and the only difference from Embodiment 2 is that the thickness of the silicon film layer is 190 nm, and the rest are the same.

[0096] Performance Test:

[0097] (1) Use a spectrometer to test the optical absorption and reflectivity of the photodetector

[0098] Test results such as Fig.13 As shown, the reflectivity of the silicon-based photodetector prepared in this embodiment at 1780nm in the near-infrared band is 35%, the absorption rate reaches 65%, and the half-maximum width of the absorption wavelength is 220nm, indicating that the silicon-based photodetector prepared in this embodiment can achieve narrow-band absorption in the 1780nm band. It can be seen that by adjusting the thickness of the silicon film layer in the photodetector prepared in Example 2, narrow-band absorption of different bands can be achieved.

[0099] (2) Study the effect of bias voltage on the responsivity of photodetectors

[0100] Fig.14 The responsivity curve of the photodetector in the near-infrared band of 1400nm to 2000nm under zero bias is a narrow-band response curve that is consistent with the trend of the optical reflectance spectrum, further indicating that the photodetector can achieve narrow-band absorption at a wavelength of 1780nm.

[0101] Fig.15 This is the responsivity curve of the photodetector in the near-infrared band of 1400nm to 2000nm under a bias of 3V. The wavelength with the highest response is still at 1780nm, the responsivity reaches 0.12A / W, the half-width of the narrow-band response peak remains at 220nm, and the gain multiple reaches 3 orders of magnitude.

[0102] In summary, the silicon-based photodetector provided by the present invention can achieve broadband or narrowband absorption of near-infrared light by adjusting the material of the top metal film layer, thereby meeting different application requirements. Moreover, the silicon-based photodetector can produce an avalanche multiplication effect when a bias voltage is applied, thereby greatly improving the light responsivity of the device, making the responsivity of the silicon-based photodetector comparable to that of commercial detectors based on germanium and indium gallium arsenide materials.

[0103] The above-described embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or changes made by those skilled in the art based on the present invention are within the protection scope of the present invention. The protection scope of the present invention shall be subject to the claims.

Claims

1. A silicon-based infrared band avalanche photodetector, characterized in that: The photodetector comprises a bottom electrode layer, a silicon film layer and a top metal film layer which are stacked in sequence; The top metal film layer forms a Schottky contact with the silicon film layer; The thickness of the silicon film layer is 10 nm-5 μm, and the material of the silicon film layer is a lightly doped n-type crystalline silicon material or a lightly doped p-type crystalline silicon material; The material of the top metal film layer is one or more of gold, silver, copper, aluminum and alloys containing at least two of the above metal elements; the top metal film layer and the bottom electrode layer form a Fabry-Perot cavity; the silicon film layer is a dielectric layer in the Fabry-Perot cavity; and the photodetector can achieve narrow-band photoelectric detection at different infrared wavelengths by adjusting the thickness of the silicon film layer; When a bias voltage is applied across the photodetector, a strong electric field is generated in the silicon film layer, and carriers gain energy in the electric field to accelerate and produce photoconductivity gain and avalanche multiplication effect, thereby increasing the photocurrent by 3-4 orders of magnitude and improving the responsiveness of the photodetector.

2. The silicon-based infrared band avalanche photodetector according to claim 1, characterized in that: The bottom electrode layer forms an ohmic contact with the silicon film layer; And / or, the material of the bottom electrode layer is selected from one or more of titanium, gold, silver, copper, chromium, and aluminum; And / or, the thickness of the bottom electrode layer is greater than 30 nm.

3. The silicon-based infrared band avalanche photodetector according to claim 2, characterized in that: The bottom electrode layer is obtained by stacking a titanium film layer, a gold film layer and an aluminum film layer in sequence, and the aluminum film layer is bonded to the silicon film layer.

4. The silicon-based infrared band avalanche photodetector according to claim 1, characterized in that: The resistivity of the silicon film layer is 0.1-100 Ω•cm.

5. The silicon-based infrared band avalanche photodetector according to claim 1, characterized in that: The thickness of the top metal film layer is 5-100 nm.

6. The silicon-based infrared band avalanche photodetector according to claim 1 or 5, characterized in that: The thickness of the top metal film layer is less than the electron mean free path; And / or, the thickness of the silicon film layer is smaller than the depletion layer width of the Schottky junction formed by the silicon film layer and the top metal film layer.

7. The silicon-based infrared band avalanche photodetector according to claim 1, characterized in that: When the material of the top metal film layer is gold, an adhesion layer is arranged between the top metal film layer and the silicon film layer; the material of the adhesion layer is selected from one or more of titanium, chromium, aluminum, and silver.

8. A method for preparing a silicon-based infrared band avalanche photodetector according to any one of claims 1 to 7, characterized in that: include: placing the pretreated silicon on the insulating layer in a hydrofluoric acid solution to remove the insulating layer to obtain the silicon film layer; A top metal film layer and a bottom electrode layer are prepared on the upper and lower surfaces of the silicon film layer respectively by physical and / or chemical methods.

9. The preparation method according to claim 8, characterized in that: The pretreatment includes a process of ultrasonically cleaning the silicon on the insulating layer with an organic solvent and water in sequence; The insulating layer is a silicon dioxide layer; The physical and / or chemical methods include magnetron sputtering deposition and electron beam evaporation.

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