PECVD amorphous silicon suboxide films for surface passivation of silicon solar cells

The surface passivation properties of hydrogenated amorphous silicon suboxides (a-SiO
_x
:H) deposited by plasma-enhanced chemical vapour deposition (PECVD) have been investigated. The process gases were nitrous oxide and a mixture of silane and helium at a deposition temperature of ~250 °C. Minority carrier lifetimes up to 270 us on 4·Ω·cm p-type float-zone silicon wafers were obtained. With thermal annealing, the carrier lifetimes of the a-SiO
_x
:H passivated silicon wafers exceed 670 us, correlating to surface recombination velocities of 30 cm/s. Optical analysis revealed a distinct decrease of light absorption in the a-SiOx:H films compared to commonly used intrinsic amorphous silicon passivation used in heterojunction solar cells.