Si-based Ge Nanowire Photodetectors

In recent years,emerging industries such as artificial intelligence,big data,and smart cities have a strong demand for infrared information detection and intelligent sensing.Infrared detectors should lightweight,low cost,low power,and high performance.Germanium(Ge)material has high carrier mobility,has a large absorption coefficient(?103/cm-1)at the optical communication wavelength(1.55 ?m),and is compatible with silicon(Si)process.Therefore,it is one of the excellent materials for preparing near-infrared photodetectors.Ge nanowire photodetectors have high photocurrent gain,but Ge nanowires grown by metal-catalyzed chemical vapor deposition methods are generally perpendicular to the substrate.So it is difficult to accurately locate and integrate Ge nanowire photodetectors,and the dark current is too high.To solve these problems,the preparation of Si-based Ge nanowires and their photodetectors by three-dimensional Ge condensation was studied.The main work content and innovations are as follows:1.Si-based Ge nanowires were prepared by Ge condensation method.Based on the three-dimensional Ge condensation model,the structural parameters of the GeSi nanowires on the insulator were calculated and designed.Si-based Ge nanowires with high crystallization quality,controllable size and position were prepared by electron beam exposure,oxidation annealing and other technological processes.2.The ATLAS module of SILVACO simulation software is used to design and simulate the Ge photoconductive detector and analyze the source of the photocurrent gain.Based on the simulation of a photoconductive detector,interface charges,interface defect states,and impurity defect states in the material are added at the interface between the oxide and semiconductor.The effects of these three defect states on the photocurrent are observed.The photogating effect is the main cause of the photocurrent gain.3.Developed Si-based Ge nanowire metal-semiconductor-metal structure photodetectors with high specific detection rate and low dark current.Ge nanowire photodetectors with different widths were developed,and it was found that the photocurrent gain of the photodetector increased from 6.31×104 to 4.47×106 as the nanowire width was reduced from 170 nm to 35 nm.With a bias of 0.51 V and a monochromatic light of 560 nm,the Ge nanowire photodetector with a width of 35 nm has a dark current as low as 5.1 nA and a specific detectivity as high as 1.26×1014 cm·Hz1/2·W-1.The ultra-high photocurrent gain of photodetector may be caused by photogating effect of oxygen vacancies in SiGeOx formed during the Ge enrichment process as electron traps.