Study On The Technology Of Broadening The Absorption Spectrum Range Of Black Silicon

Black silicon(B-Si)is widely used in solar energy collection and photodetectors due to its excellent light trapping performance and wide spectrum absorption.However,under the influence of silicon band gap width(E_g=1.12ev),the spectral absorption of generalized B-Si is rapidly reduced above 1100nm.Although the infrared absorption performance of B-Si can be improved by optimizing the structure or introducing impurity energy level,the limited improvement still restricts the application of B-Si in the infrared band.To further promote the application of B-Si,it has become a hot topic how to broaden the absorption spectrum range of the B-Si.In this paper,the micro-nano metallic structures are prepared on the surface of B-Si,and the absorption spectrum range of B-Si is widened by the local surface plasmon effect,which induced by the micro-nano metallic structure under the action of the light field.According to the research scheme from simulation to experiment.Firstly,through step-by-step simulation,the simulation models of covering B-Si with various micro-nano metallic structures were built,and the optical performance were analyzed.In the experiment,the method of one-step preparation of micro-nano metallic structure on the surface of B-Si by using"double shadowing effect"was proposed,which significantly improved the near-infrared light absorption performance of B-Si;Finally,the Si-PIN photodetector based on plasmon composite B-Si is trial-produced,and the key parameters of the photodetector are tested and analyzed.The research results are as follows:1.The structure of the B-Si model determines its basic light trapping performance,and its light trapping performance is adjustable due to the change of structural dimensions.By increasing the depth of the B-Si model,its infrared absorption performance can be significantly improved.2.The coverage of nano-metallic particles can improve the infrared absorption performance of the B-Si model,and the material type,size,number and distribution density of the particles can affect the band of absorption light.3.The cone-hole B-Si with upper"needle"and lower"hole"is formed by reaction ion etching,which has the absorptivity of 98.7%in the visible light range.The visible light absorption of bowl-hole B-Si is stable,is about 80%.However,the absorption rate of these B-Si light-trap structures is only 15~20%in the spectral above the silicon bandgap.4.By controlling the process of film growth and taking advantage of the shadowing effect in the deposition process,the micro-nano metallic structure can be prepared on the surface of B-Si in one step,and the infrared absorption performance of B-Si can be significantly improved.Among them,in the spectral range of 1100nm~2500 nm,the bowl-hole-B-Si/10 nm Au has 41.5%average absorption rate,and the bowl-hole-B-Si/10nm TiN has 67.6%average absorption rate;in the spectral range of 350~2500 nm,the cone-hole-B-Si/40 nm Au has 96.5%average absorption rate,and the cone-hole-B-Si/50nm TiN has 97.1%average absorption rate.5.The spectral response range of Si-PIN photodetector based on plasmonic complex B-Si(bowl-hole-B-Si/TiN)is 300~1170 nm,the peak response is 0.64A/W(@980nm,180V),the 1060 nm response rate is 0.45 A/W(EQE=52.6%,180 V),and the dark current is less than 10 nA.