Studies Of A-Si:H Microstructure By Hot Wire Assisted Mwecr CVD Technique

Amorphous silicon (a-Si) has the special characteristic on structure, made a-Si has special optical and electronic characteristics, so it had huge prospect of application. But there are a lot of defects (dangling band) in amorphous silicon, therefore its application have been limited. To hydrogenated amorphous silicon (a-Si:H), however, it has much less defects than non-hydrogenated a-Si, for the sake of much hydrogen which eliminate the defects by making a bond with non-connected Si bond. With these virtue, a-Si:H accord with device quality. The films of a-Si:H have widely used in solar cell field. But the deposition rate and quality of a-Si:H was primarily affected by preparation methods. In view of its virtue of high degree of electron and ion generations, hot wire assisted hot wire assisted the microwave electron cyclotron resonance (MWECR) CVD is expected to deposit device quality a-Si:H at high deposition rate. Thus, we have prepared a-Si:H films under diverse conditions using hot wire assisted MWECR CVD. We deposit the high quality a-Si:H by MWECR CVD method in laboratory. The dissertation mainly focuses on variation of the structure of a-Si:H as functions of the hot wire temperature, and found that proper hot wire temperature is favorable to hydrogen elimination and thus improve the structure of films. The speciality of a-Si:H films is closely associated with hydrogen content in films. On the one hand, hydrogen incorporated as monohydride (Si-H) saturates dangling bonds in films, and on the other hand, hydrogen incorporated as polyhydride (Si-H2,Si-H3, (Si-H2)n) introduces defect in films and thus increases the density of localized electronic states in band gap. The transmission spectra of films are converted to the absorption spectra in terms of reasonable baseline. We obtained hydrogen content and bonding configurations of films by analyzing the integrated absorbance of the wagging mode and stretching mode. We found that hydrogen content incorporated as monohydride and hydrogen content incorporated as polyhydride gradually decreases with the increase of hot wire temperature. We also take a series of testing on Raman spectra, which analyzing the situation in different hot wire temperature and different anneal process. As the increasing in hot wire temperature, it turns out to be a mixture state of a-Si /u-Si. At the same time, we...