Boron Doped a-SiO_x:H Prepared by H₂ Diluted SiH₄+CO₂ Plasma

摘要

This paper reports the preparation of hydrogenated amorphous silicon oxide (a-SiOx:H) thin films byusing plasma enhanced chemical vapor deposition (PECVD) technique at various doping ratios ofdiborane/silane(RB=[B2H6]/[SiH4]=0% 0.75% 1.5% 4.5% 7.5%), and different carbondioxide/silane gas flow ratios (RC=[CO2]/[SiH4]=0 and 1) at a substrate temperature of 200(TS =200, a process pressure of 220Pa, a hydrogen dilution ratio (RH=[H2]/[SiH4]=200) and a power-2 density of 1Wcm . We investigated the effect of various borane doping concentration on themicrostrcture, optical and electrical properties of as prepared p-type a-SiOx:H thin films via Ramanspectroscopy, X-ray diffraction spectrum, ultraviolet visible light transmission spectrum (UV-VIS) andvariable temperature resistance measurement method. It was found that, with the increasing of borondoping ratios, the optical band gap decreases but the refractive index increases. The dark conductivityof doped amorphous films increases monotonously with the increasing of boron doping content, whilethe dark conductivity of doped a-SiOx:H films is not only determined by the concentration of dopantbut also the crystallinity and oxygen content of the films. As increasing RB, the crystallinity of dopedc-Si:H and a-SiOx:H films simultaneously decreases, which causes the decrease of dark conductivity.-1 -1Finally, B-doped a-SiOx:H thin films with a highest dark conductivity of 0.048 cm have beprepared.