ROLE OF ATOMIC-HYDROGEN FOR THE FORMATION OF NETWORK STRUCTURE OF AMORPHOUS SIGE ALLOY - COMPARISON OF THEORETICAL PREDICTIONS AND EXPERIMENTAL RESULTS

The influence of systematic variation of hydrogen dilution and rf powe r density and their inter correlation on the optoelectronic and struct ural properties as well as defect densities of amorphous silicon germa nium (a-SiGe:H) alloy deposited in ultra high vacuum (approximate to 1 0(-9) Torr) plasma enhanced chemical vapor deposition (PECVD) system h ave been investigated. It has been observed that low hydrogen dilution of source,eases (silane and germane) during the growth of films impro ves the resulting properties whereas high dilution has the opposite ef fect. The optimal value of hydrogen dilution for relaxed network struc ture of a-SiGe:H alloy is very much linked with rf power density. The variation of film properties with plasma condition during its growth n icely corroborate Street's hypothesis on optimal growth condition for amorphous silicon and its alloys, based on hydrogen density of states (HDOS). This work also indicates that metastable hydrogen (H) has a v ital role to transport energy to the matrix for its requisite structur al relaxation apart from its chemical activity.