Simulation of semiconductor nanowire photodetectors with high photoconductive gain

Abstract

Abstract In this paper, first we simulate the light absorption of individual cylindrical nanowire with the diameter ranging from 100to 300 nm, it is found that the absorption peak has a red-shift along with the increased diameter. Then some numericalsimulations have been done to elucidate the high gain mechanism and investigate the dependence of photoconductive gain on various parameters, such as doping, surface state de nsity, and structure. The results show that optimizing theseparameters appropriately can lead photoconductive gain up to 10 6 , and give a reliable guiding to the actual device design. Key words : nanowire, surface states, photoconductive gain, simulation  Introduction Photodetectors are a primary element in extensive applications. With the development of technology, the sustained scaling of photodetector devices has brought one-dimensional nanowire structures into the forefront of research. Semiconductor nanowire photodetectors show a high photoconductive gain and attract too much attention in consequence of their unique properties arising from the nanowire geometry. Semiconductor materials are often used to build photodetector devices. Silicon is a splendid candidate due to its low cost, ease of processing and ability forintegration with conventional fabrication techniques, and germ anium is also an excellent candidate because of its highcarrier mobility, small bandgap and compatibility with silicon. This work is aiming at investigating the properties of Si and Ge NWs, and taking advantage of them to create a very high photoconductive gain sensitive to a wide range ofwavelengths from the ultraviolet to the near infrared spectrum. Some numerical simulations have been done to elucidatethe high gain mechanism and investigate the dependence of photoconductive gain on various parameters, such as doping, surface state density, and structure.