Preparation And Properties Of Hyper-doped Silicon With Deep-level Impurities

Silicon hyper-doped with deep-level impurities is a key technology for preparing intermediate-band solar cells,a kind of new-generation solar cells with high efficiency.However,at present,traditional hyper-doping methods such as ion implantation combined with pulsed laser melting have disadvantages such as low doped layer thickness,uneven impurity distribution,and high preparation cost.Therefore,it is necessary to develop a new method that can effectively perform hyper-dopingofdifferentdeep-levelimpuritiesinsiliconwith controllable thickness of hyper-doped layer and convenient preparation process.In this work,the silicon films hyperdoped with deep-level impurities including titanium,silver and iron have been prepared by vacuum magnetron sputtering and nanosecond pulsed laser melting.X-ray photoelectron spectroscopy analysis shows that the titanium or silver doped silicon material has a very high impurity doping concentration and achieves hyper-doping,and the thickness of the hyper-doping layer is high?above 200 nm?.This result has a significant improvement compared with the traditional hyper-doping process.The spectra of glancing incidence X-ray diffraction pattern show that the thin film layer of impurity-doped silicon is polycrystalline structure after pulsed laser melting.The highest crystallinity of sample is almost to 25%around.The infrared light absorption measurement shows that the hyperdoped silicon samples have high absorptivity with obvious characteristics of sub-band absorption in wavelength larger than 1200nm.The infrared light absorption coefficient of samples is more than1×10³cm^-1,and the highest absorption coefficient is almost to 5×10³cm^-11 which is far more than that of monocrystalline silicon without doping.The Hall effect measurements show that the thin film layer of titanium doped silicon has high carrier concentration,over 5×10¹⁸cm^-3around.This value of carrier concentration of thin film samples is higher than that of titanium hyper-doping in silicon.The sheet resistance of samples is lower than that of monocrystalline silicon.The infrared light absorptivity is positively correlated with the crystallinity and the carrier concentration of the silicon thin films.This new method of vacuum magnetron sputtering combined with 532 nm wavelength pulsed laser melting could be an effective way for deep energy level impurity hyper-doping with high infrared absorption.