Extremely Low Surface Recombination Velocities Realized by Cat-CVD SiNx/a-Si Staked Films on (100) and (111) Crystalline Si Substrates

Abstract

The surface recombination velocity (SRV) of alkali-textured crystalline silicon (c-Si) wafers can be lowered to as low as 4.8 cm/s by using amorphous Si (a-Si) and Si nitride (SiNx) stacked films prepared by catalytic chemical vapor deposition (Cat-CVD). This value is much lower than those of c-Si wafers passivated by similar stacked structures formed by remote plasma-enhanced CVD (PECVD). It is revealed that the plasmadamage- less deposition of Cat-CVD a-Si insertion layers plays an important role to improve interface quality, and also that SiNx films are also essential for the dramatic reduction of SRV down to such low levels. We also investigate the interface of a-Si/c-Si using a scanning transmission electron microscope (STEM) in order to clarify the origin of a sensitive dependence of SRVs of the stacked structure on the thickness of an a-Si layer. We find remarkably close correlation of the results of the STEM observation and SRVs.