Optimization of glow discharge deposition of amorphous silicon solar cells

The transient plasma emission spectrum of the RF glow discharge of silane and its effects on the optoelectrical properties of a-Si:H films are studied. It is shown that a certain time is required for the plasma emission intensities to reach equilibrium. The samples prepared in the transient state were characterized by an excess hydrogen content with higher SiH₂ bonding configurations and a blue shift of the optical gap with a decrease in photoluminescence intensity in comparison with samples prepared in the equilibrium state. It is demonstrated that there exists an initial nonequilibrium stage in the plasma-enhanced chemical vapor deposition process, which is detrimental to the properties of the deposited amorphous silicon thin films. It can be improved by raising the RF power or increasing the gas flow rate during the deposition process.