Silicon-based room temperature infrared photoelectric detector and manufacturing method thereof

Abstract

The present invention provides a silicon-based room temperature infrared photodetector and a method for making the same, and belongs to the field of semiconductor and photoelectric detection technology. The manufacturing method comprises: completing ion implantation of the substrate by injecting chalcogen ions; annealing the injected sample by pulsed laser melting to achieve recrystallization of the injected layer; making interdigitated gold electrodes on the injected layer by photolithography, electron beam evaporation and stripping processes; using indium / gallium alloy to form an ohmic contact on the back of the substrate as the back electrode of the photodetector, and finally obtaining the photodetector. Since the super-doped silicon layer prepared by super-doping of chalcogen elements has ultra-high carrier density and thermal stability, and does not show lattice mismatch; and the prepared photodetector shows strong performance indicators, such as responsivity, specific detection rate, bandwidth and response speed, it provides a feasible method for realizing a new generation of silicon-based room temperature infrared photodetectors with wide spectral response and high detection rate in the future.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor and photoelectric detection, and particularly relates to a silicon-based room temperature infrared photoelectric detector and a manufacturing method thereof. Background Art

[0002] Silicon material is the material basis of integrated circuits and an important pillar material of the contemporary information industry. The development and replacement of transistors to computers and even the development and progress of current communication networks are closely related to silicon single crystals. Its quality and size are also constantly improving. Silicon-based electronic products have penetrated into various disciplines and fields. Silicon-based optoelectronic technology has the advantages of high speed, low cost, low loss and high integration, and can develop photonic systems compatible with complementary metal oxide semiconductors (CMOS). It is facing a historical opportunity for large-scale industrialization and marketization, and is one of the most promising technology fields in today's era. However, for photodetectors integrated in photonic circuits with wavelengths exceeding 1100 nm, silicon materials are limited by their bandgap width (1.12 eV), and their infrared light response is fundamentally limited to the near-infrared range. Therefore, the development of room-temperature broadband infrared silicon-based photodetectors is of great significance in the field of silicon-based optoelectronic systems.

[0003] At present, one of the most effective ways to further extend the room-temperature photoresponse of silicon to the mid- and short-wave infrared range is to dope deep-level impurities (such as transition metals and chalcogens) in silicon at a concentration exceeding the solid solubility limit. This process introduces an intermediate band, namely the impurity energy level, between the conduction band and the valence band of the silicon material, thereby achieving the absorption of photons with energy lower than the silicon band gap. Therefore, deep-level impurities can also be used to obtain infrared silicon-based photodetectors that work at room temperature, which is impossible with shallow-level impurities. However, deep-level impurities such as transition metals diffuse very quickly in silicon. As a result, they diffuse to the silicon surface, causing solute segregation and lattice mismatch, hindering the incorporation of doping impurities, and ultimately making it impossible to manufacture devices compatible with CMOS systems. In addition, the sub-bandgap absorption rate of non-equilibrium doped silicon will decay with the thermal annealing process, and the degree of this sub-bandgap absorption annealing attenuation is directly related to the impurity elements doped, which will affect the compatibility of deep-level impurity super-doped silicon with some existing CMOS system preparation processes (involving high-temperature annealing-related steps). Since the diffusion rate of chalcogen impurities is much lower and the super-doped silicon layer prepared by super-doping of chalcogen elements has ultra-high carrier density and thermal stability, chalcogen-superdoped silicon is expected to manufacture photodetectors with wide spectral response and higher detectivity and apply them to the manufacturing process. Summary of the invention

[0004] The purpose of the present invention is to solve the technical problems that the current photoelectric detectors made of silicon materials have low response efficiency in the infrared band, high cost, and are not compatible with CMOS systems, and to provide a silicon-based room temperature infrared photoelectric detector and a method for manufacturing the same.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A silicon-based room-temperature infrared photodetector, comprising: a chalcogenide super-doped silicon layer, a substrate, a top electrode and a bottom electrode; the substrate is a P-type silicon substrate, the chalcogenide super-doped silicon layer and the substrate form a PN junction; the chalcogenide super-doped silicon layer has a thickness of 120 nm, has an ultra-high carrier density and thermal stability, the top electrode is an interdigitated gold electrode, the spacing and thickness of which are 5 μm and 200 nm respectively, the top electrode forms an ohmic contact with the chalcogenide super-doped silicon layer, the bottom electrode is located at the bottom of the substrate, and the bottom electrode is made of an indium / gallium alloy.

[0007] A method for manufacturing a silicon-based room temperature infrared photodetector is provided, the steps of the method comprising:

[0008] S1. Ion implantation of the substrate is completed by implanting chalcogen ions;

[0009] S2. Annealing the injected sample by pulsed laser melting to achieve recrystallization of the injected layer;

[0010] S3. Fabricate interdigitated gold electrodes (top electrodes) on the implantation layer by photolithography, electron beam evaporation, and lift-off;

[0011] S4. Use indium / gallium alloy to form an ohmic contact on the back side of the substrate to serve as the back electrode of the photodetector, and finally obtain the silicon-based room temperature infrared photodetector.

[0012] Furthermore, in step S1, during the chalcogen ion implantation, two consecutive implantations with an implantation energy ratio and an implantation dose ratio of 2.5:1 are performed into the substrate to obtain uniformly distributed chalcogen impurities in the implantation layer.

[0013] Furthermore, in step S1, the implantation of chalcogen ions into the substrate further includes realizing chalcogen element super-doped silicon at room temperature infrared response, and the specific steps are:

[0014] 1) By implanting chalcogen ions into the substrate material; the implantation dose is (0.78-6.2)×10 15 cm −2 Sum (3.1-25) × 10 14 cm −2, joint implantation with implantation energies of 150 and 50 keV, respectively, introduces an intermediate band between the conduction band and the valence band of the silicon material;

[0015] 2) For photons with energy below 1.12 eV, charge carriers are excited from the valence band through the intermediate band to the conduction band, achieving room-temperature infrared response and completing the production of chalcogenide-superdoped silicon.

[0016] Furthermore, in step S2, the implantation layer annealing treatment is pulsed laser melting to complete the activation of impurities and the regrowth of the epitaxial layer.

[0017] Furthermore, in step S3, before preparing the interdigitated gold electrode, the silicon dioxide on the surface of the chalcogenide super-doped silicon layer is etched away by hydrofluoric acid, and then a 200 nm thick interdigitated gold electrode is prepared on the super-doped silicon layer by photolithography, electron beam evaporation and stripping process.

[0018] The beneficial effects of the present invention are:

[0019] (1) The ultra-doped silicon layer prepared by ultra-doping with chalcogen elements has ultra-high carrier density and thermal stability, and does not show lattice mismatch;

[0020] (2) The prepared photodetectors exhibit strong performance indicators, such as responsivity, specific detectivity, bandwidth, and response speed;

[0021] (3) This provides a feasible method for realizing a new generation of silicon-based room-temperature infrared photodetectors with wide spectral response and high detectivity in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the process of silicon-based room temperature infrared photodetector and its manufacturing method;

[0023] Figure 2 (a) and (b) are the structural schematic diagram and longitudinal cross-sectional schematic diagram of the chalcogenide super-doped silicon photodetector, respectively;

[0024] Figure 3 Schematic diagram of dark current-voltage curve and light-irradiation current-voltage curve of the chalcogenide super-doped silicon photodiode prepared in this embodiment at room temperature;

[0025] Figure 4 A schematic diagram of the spectral response rate of the chalcogenide super-doped silicon photodiode prepared in this embodiment at room temperature measured under zero bias;

[0026] Figure 5 is the relative detection rate of the chalcogenide super-doped silicon photodetector prepared in this embodiment and the commercial photodetector at 300 K and 77 K, that is, D * Comparison diagram;

[0027] Figure 6 Schematic diagram of transient photocurrent measured at different temperatures for the chalcogenide super-doped silicon photodetector prepared in this embodiment under an LED pulse light source with an incident light intensity of 0.11 mW and a frequency of 1 kHz. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0029] See also Figure 1-Figure 2 , this embodiment provides a:

[0030] like Figure 1 As shown, a silicon-based room temperature infrared photodetector and a method for making the same are provided. The steps of the method for making the photodetector are as follows: (1) during ion implantation, two consecutive implantations with an implantation energy ratio and an implantation dose ratio of 2.5:1 are used to obtain uniformly distributed chalcogenide impurities in the implantation layer, and then the activation of the impurities and the regrowth of the epitaxial layer are completed by pulsed laser melting; (2) before preparing the contact electrode, the silicon dioxide on the surface of the super-doped silicon layer needs to be etched away by hydrofluoric acid. Then, a 200 nm thick interdigitated gold top electrode is prepared on the super-doped silicon layer by photolithography, electron beam evaporation and stripping processes; (3) an indium / gallium alloy is used to form an ohmic contact on the back of the substrate as the back electrode of the photodetector, and finally a photodetector is obtained.

[0031] like Figure 2 As shown in the figure, the silicon-based room-temperature infrared photodetector device includes a chalcogenide super-doped silicon layer, a P-type silicon substrate, a top electrode and a bottom electrode; the chalcogenide super-doped silicon layer with ultra-high carrier density and thermal stability has a thickness of 120nm and forms a PN junction with the P-type silicon substrate; the top electrode is an interdigitated gold electrode with a spacing and thickness of 5 μm and 200 nm respectively, the top electrode forms an ohmic contact with the chalcogenide super-doped silicon layer, and the indium / gallium alloy bottom electrode is located at the bottom of the P-type silicon substrate. Figure 2 (a) Schematic diagram of the structure of chalcogenide super-doped silicon photodetector; Figure 2 (b) Schematic diagram of the longitudinal section of the chalcogenide super-doped silicon photodetector.

[0032] In this embodiment, chalcogenide elements can be used to hyper-dope silicon: (1) by doping chalcogenide elements into the silicon substrate material, an intermediate band (also called impurity energy level) can be introduced between the conduction band and the valence band of the silicon material; (2) for photons with energy below 1.12 eV, charge carriers are excited from the valence band through the intermediate band to the conduction band (valence band → intermediate band and intermediate band → conduction band), thereby achieving room temperature infrared response.

[0033] Impurity level modulation theory of silicon-based room temperature infrared photodetectors, through super doping (or non-equilibrium doping), supersaturated impurities can be introduced into crystalline silicon. This process can change the energy band structure of silicon and increase the light absorption coefficient of silicon, especially the sub-bandgap light absorption coefficient. Usually, the effect of super doping on the light absorption coefficient of semiconductor materials is achieved by introducing a large number of new defect energy level states, by introducing a large number of deep energy level defect centers in the bandgap of silicon, and these defect centers can enhance the material's light absorption coefficient in the bandgap and sub-bandgap bands.

[0034] Doping crystalline silicon with low concentrations of chalcogenide impurities will introduce a large number of discrete localized donor energy levels (originating from a large number of point defects, dimers and other complex structures) in the bandgap of silicon within 100-300 meV below the bottom of the conduction band. As the concentration of chalcogenide impurities increases, new atomic structures may form in crystalline silicon, and the positions of these discrete energy levels may move and broaden. The wave functions of these deep energy level centers may overlap to form a delocalized intermediate band (impurity energy level).

[0035] The formation of the intermediate band can serve as a step to assist the absorption of sub-bandgap photons. For photons with energy below 1.12 eV, electron excitation from the valence band to the intermediate band and from the intermediate band to the conduction band is also feasible. Therefore, the formation of the intermediate band (or intermediate energy level) is very likely to be the root cause of the extended sub-bandgap absorption in super-doped silicon. This embodiment uses chalcogenide super-doped silicon: (1) by doping chalcogenide elements into the silicon substrate material, an intermediate band (also called an impurity energy level) can be introduced between the conduction band and the valence band of the silicon material; (2) for photons with energy below 1.12 eV, charge carriers are excited from the valence band through the intermediate band to the conduction band (valence band → intermediate band and intermediate band → conduction band), thereby achieving room temperature infrared response.

[0036] In this embodiment, a room-temperature infrared photodetector is designed for silicon-based devices. The super-doped silicon layer prepared by super-doping with chalcogen elements has ultra-high carrier density and thermal stability, and does not exhibit lattice mismatch; and the prepared photodetector exhibits strong performance indicators, such as responsiveness, specific detection rate, bandwidth and response speed.

[0037] See also Figure 3 , at a light intensity of 20 mW cm -2The current-voltage curve of the chalcogenide super-doped silicon photodiode prepared in this embodiment at room temperature under the conditions of white light illumination and light avoidance. Figure 3 As shown in the figure, the prepared chalcogenide super-doped silicon photodiode exhibits an obvious diode rectification effect. At a bias voltage of ±0.5 V, the forward / reverse current ratio is 357. By fitting the dark current-voltage curve using a single diode equation, the diode rectification effect is further analyzed:

[0038] I = I 0 [ e q ( V − IR s ) η k B T − 1 ] + V − IR S R Shunt ;

[0039] Where I0 is the saturation current, q is the electron charge, η is the diode ideality factor, and k B is the Boltzmann constant, T is the temperature; and R s and R shunt are the series resistance and the parallel resistance, respectively. By fitting the experimental data, it is found that the ideal factor at room temperature is 2.1. The rectifying effect of this diode is directly related to the N-type characteristics of chalcogenide superdoped silicon, and a PN junction is formed between the P-type silicon substrate and the N-type chalcogenide superdoped silicon layer. Under a reverse bias voltage of -50 mV, the room temperature dark current density of the chalcogenide superdoped silicon photodiode is 0.2 mA / cm -2 , which is lower than the reported gold-doped silicon and selenium-doped silicon photodetectors. Under white light illumination, due to the working principle of the photodetector, the reverse current of the photodiode suddenly increases by more than an order of magnitude, which infers that the open-circuit voltage is about 0.2 V.

[0040] Figure 4 The spectral response rate of the chalcogenide super-doped silicon photodiode prepared in this embodiment measured at zero bias at room temperature is given. Among them, Figure 4 Also included is the room temperature spectral responsivity of a commercial Si-PIN photodiode (model: BPW34) ( Figure 4 dotted line) for comparison.

[0041] See also Figure 4 The chalcogenide super-doped silicon photodiode prepared in this embodiment exhibits a strong sub-bandgap photoelectric response in the 5 μm wavelength range, while the responsivity of the commercial silicon photodetector used as a comparison reaches a response cutoff when the wavelength exceeds 1.2 μm. At a wavelength of 1.12 μm, the room temperature photoelectric responsivity of the chalcogenide super-doped silicon photodiode is 79 mA W -1 In addition, its room temperature responsivity is about 0.3 mA W in the 1.55 μm communication band. -1 , which means that the response level of the chalcogenide super-doped silicon photodiode prepared in this embodiment is equal to that of the current super-doped silicon-based photodiodes and solar cells at this wavelength.

[0042] See also Figure 5 At 300 K and 77 K, the D of the chalcogenide super-doped silicon photodetector prepared in this example is significantly different from that of the commercial photodetector. * (Specific Detection Rate) for comparison. Figure 5 It can be seen that in the wavelength range of 1.0-1.9 μm, the room temperature D * The D * This is about three orders of magnitude lower than that of commercial Ge photodiodes (i.e., FDG03).

[0043] See also Figure 6 For photodetectors, in addition to photoelectric responsivity, the transient response characteristics (response speed) of the device are also very important performance indicators. Figure 6 The figure shows the time-varying light response of the photodetector under pulsed light with an incident light intensity of 0.11 mW and a frequency of 1 kHz at different temperatures, and records its transient response current. It can be seen that under the change of temperature, the chalcogenide super-doped silicon photodetector prepared in this embodiment still has obvious and repeatable switching phenomena, which indicates that the chalcogenide super-doped silicon photodetector has a stable working mechanism under pulsed light, and the room temperature response time of the rising process measured when the bias voltage is zero is only 39 μs.

[0044] The super-doped silicon layer prepared by super-doping of chalcogen elements in this embodiment has ultra-high carrier density and thermal stability, and does not show lattice mismatch; and the prepared photodetector shows strong performance indicators, such as responsivity, specific detection rate, bandwidth and response speed; the obtained photodetection performance indicators are comparable to the values ​​obtained by commercial photodetectors; and its photodetection performance indicators can be further improved by optimizing the manufacturing process. For example, by optimizing the device structure through appropriate surface passivation, improving the design of the optically active region for absorption, improving the geometry of the metal electrode for carrier collection, and improving the anti-reflection coating, etc., it provides a feasible method for realizing a new generation of silicon-based room temperature infrared photodetectors with wide spectral response and high detection rate in the future.

[0045] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A silicon-based room temperature infrared photodetector, characterized in that: The silicon-based room-temperature infrared photodetector comprises: a chalcogenide super-doped silicon layer, a substrate, a top electrode and a bottom electrode; the substrate is a silicon substrate, and the chalcogenide super-doped silicon layer forms a PN junction with the substrate; the chalcogenide super-doped silicon layer has a thickness of 120 nm, the top electrode is an interdigitated gold electrode, the spacing and thickness of which are 5 μm and 200 nm respectively, the top electrode forms an ohmic contact with the chalcogenide super-doped silicon layer, the bottom electrode is located at the bottom of the substrate, and the bottom electrode is made of an indium / gallium alloy.

2. A method for manufacturing a silicon-based room temperature infrared photodetector, characterized in that: The steps of the method are: S1. Ion implantation of the substrate is completed by implanting chalcogen ions; S2. Annealing the injected sample by pulsed laser melting to achieve recrystallization of the injected layer; S3. Fabricating interdigitated gold electrodes on the implantation layer by photolithography, electron beam evaporation, and lift-off; S4. An indium / gallium alloy is placed on the back side of the substrate to form an ohmic contact to serve as the back electrode of the photodetector, and finally the silicon-based room temperature infrared photodetector is obtained.

3. The method for manufacturing a silicon-based room temperature infrared photodetector according to claim 2, characterized in that: In step S1 , during the chalcogen ion implantation, two consecutive implantations with an implantation energy ratio and an implantation dose ratio of 2.5:1 are performed into the substrate to obtain uniformly distributed chalcogen impurities in the implantation layer.

4. The method for manufacturing a silicon-based room temperature infrared photodetector according to claim 2, characterized in that: In step S1, the implantation of chalcogen ions into the substrate also includes infrared response at room temperature for realizing chalcogen element super-doped silicon, and the specific steps are: 1) By implanting chalcogen ions into the substrate material; the implantation dose is (0.78-6.2)×10 15 cm −2 Sum (3.1-25) × 10 14 cm −2 , joint implantation with implantation energies of 150 and 50 keV, respectively, introduces an intermediate band between the conduction band and the valence band of the silicon material; 2) For photons with energy below 1.12 eV, charge carriers are excited from the valence band through the intermediate band to the conduction band, achieving room-temperature infrared response and completing the fabrication of chalcogenide-superdoped silicon.

5. The method for manufacturing a silicon-based room temperature infrared photodetector according to claim 2, characterized in that: In step S2, the implantation layer is annealed by pulsed laser melting to complete the activation of impurities and the regrowth of the epitaxial layer.

6. The method for manufacturing a silicon-based room temperature infrared photodetector according to claim 2, characterized in that: In step S3, before preparing the interdigitated gold electrode, the silicon dioxide on the surface of the chalcogenide super-doped silicon layer is etched away by hydrofluoric acid, and then a 200 nm thick interdigitated gold electrode is prepared on the super-doped silicon layer by photolithography, electron beam evaporation and stripping process.

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