5 - Optoelectronic Properties of Amorphous Silicon Using the Plasma-Enhanced Chemical Vapor Deposition (PECVD) Technique

Abstract

The aim of this chapter is to study optoelectronic properties of amorphous silicon using the plasma-enhanced chemical vapor deposition (PECVD) technique. The most intensively studied of the amorphous semiconductor family is amorphous silicon (a-Si), and particularly the hydrogenated variety. Any deposition technique that does not employ a reactive environment of H (or F) leads to extremely poor materials in terms of high density of localized states (DOS) due to Si dangling bonds, such that the films cannot be electronically doped, which then precludes any electronic device possibilities. Numerous techniques for depositing a-Si-based alloys have been attempted, plasma-enhanced chemical vapor deposition (PECVD) in SiH4 gas, PECVD in SiF4 and H2 gas mixtures, reactive sputtering of Si in H environments, evaporation of Si in the presence of H, CVD of SiH4 gas and higher silanes, photo-CVD, electron cyclotron resonance (ECR) PECVD, and remote PECVD. This chapter attempts to show that an interdependence exists among crucial deposition parameters and their influence on the material properties and hence on the performance of the electronic devices. Amorphous silicon technology has now matured to the point where many products are now commercially available.