Relaxation of thermally induced defects in LPCVD amorphous silicon

Thermally induced metastability has been studied on P doped LPCVD a-Si (low pressure chemical vapour deposited amorphous silicon) films as a function of the concentration of hydrogen in these films. The hydrogen concentration has been varied over two orders of magnitude, from 0.06 at.% in as-deposited films to 15 at.% in heavily implanted films. We find that thermal metastability effects are present even at the lowest concentrations of hydrogen. These become larger as hydrogen concentration increases. Our studies indicate that hydrogen plays an important role in thermal equilibration of a-Si:H and supports the hydrogen glass model.