| Photoelectric conversion is the core of many technologies in our daily life,and photodetectors are an essential and important part of many devices.With the development of microelectronic technology,Schottky heterojunction photodetectors based on metal and semiconductor silicon are considered to have broad application prospects due to their simple manufacturing process,good stability,and more importantly,the good compatibility with semiconductor processes,etc.However,due to the high reflectivity and low absorption of infrared light of its electrode material,the detection efficiency of Schottky heterojunction photodetectors is reduced,and the detection wavelength is mainly concentrated below 1650 nm,which limits its detection in infrared.As a direct narrow-bandgap semiconductor,Indium Antimonide,the heterojunction detector device formed with silicon can exert the advantages of energy band matching,which can make up for the above shortcomings.In this paper,an InSb/Si heterojunction photodetector that can be detected in a wide band was prepared by growing an InSb thin film directly on a silicon substrate.First,the properties of the InSb thin film and the light and temperature response characteristics of the InSb/Si device were studied.Then,the introduction of graphene as a surface transparent electrode was used to improve the transmission efficiency of photogenerated carriers and the response speed of the device.The performance of Gr/InSb/Si heterojunction photodetectors was studied.The main research contents and conclusions include:?1?Preparation and characterization of InSb thin films.The InSb thin film was grown by a simple thermal evaporation method.Combined with the existing instruments in the laboratory,the surface morphology and structure of the InSb thin film were characterized and simply analyzed by Scanning Electron Microscope,Raman spectroscopy,X-ray Diffraction analysis,Atomic Force Microscope,and Fourier Transform Infrared spectrometer.The prepared InSb thin film is continuously and uniformly distributed on the substrate,with a thickness of about 20 nm,and has strong absorption at a wavelength of1.2?m,and the absorptivity in the near infrared band is about 30%.?2?Performance test of InSb/Si heterojunction photodetector devices.The InSb/Si heterojunction photodetector device was prepared by directly growing an InSb thin film on a silicon substrate,and its photoelectric performance was tested.In the visible light band,using a 635 nm laser,when the incident optical power is 450?W,the device has a dark current of 8.7×10-10 A and a photocurrent of 2.54×10-6 A.The corresponding switching ratio is 2.9×103,the responsivity is 5.6 mA/W,the specific detection rate is 6.7×10100 cm Hz1/2/W,and the response speed is fast,with high stability and repeatability.There is also a significant light response in the infrared band.Under the light source of 1550 nm wavelength,when the power is 130 mW,the switching ratio of the device is 62,the responsivity is 8.8×10-4 mA/W,and the specific detection rate is 7.2×106 cm Hz1/2/W.Under the irradiation of 2700 nm laser,when the power is 8.5 mW,the switching ratio of the device is 3,the responsivity is 6.4×10-4 mA/W,and the specific detection rate is4.3×106 cmHz1/2/W.By testing the response of the device at different temperatures,the results show that as the operating temperature increases,the on/off ratio of the device decreases and performance deteriorates.?3?The reasons for the poor performance of InSb/Si devices were analyzed,and a method of adding graphene as a surface transparent electrode to enhance the device performance was proposed.The performances of the three structures?InSb/Si,Gr/InSb/Si,Gr/Si?are compared,and the conclusions are as follows:The combination of the InSb thin film and the silicon substrate broadens the working band of the Gr/Si detector.The addition of graphene significantly increased the photocurrent of the InSb/Si device,thereby improving the device's responsiveness,specific detection rate and response speed.Among them,the performance of Gr/InSb/Si is the best,and the supplementary tests are performed.The 3dB cut-off frequency of the device is about 172 kHz,which is 12 orders of magnitude higher than the similar devices reported previously.The device has excellent linearity under 635 nm light,and at 1550 nm,the device's responsivity decreases with increasing incident light power.Based on the measured dark current noise,the equivalent noise power is 8.7×10-12 W Hz-1/2,and the specific detection rate is 2.3×1010 cm Hz1/2/W.The specific detection rate and equivalent noise power obtained based on the calculated values of dark current noise are 1.9×1012 cm Hz1/2/W and 1.05×10-13 W Hz-1/2,respectively.The principle that the graphene surface electrode enhances the performance of silicon-based compound semiconductor photodetector devices is discussed,which provides new ideas for the development of infrared high-efficiency photodetector devices. |
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