WIDE-BAND GAP AMORPHOUS SILICON-BASED ALLOYS

Wide band gap a-SiC:H and a-SiN:H films have been deposited by ultra h igh vacuum plasma enhanced chemical vapor deposition. For a-SiC:H film s SiH4 + CH4, SiH4 + CH4 + H-2 and SiH4 + C2H2 gas mixtures have been used, whereas for a-SiN:H films SiH4 + NH3 gas mixtures have been empl oyed. The deposition conditions have been chosen for all the feedstock s to allow the growth of high electronic quality materials, in order t o reach a complete understanding of analogies and differences in techn ological and physical characteristics of the two alloys, which is nece ssary for a more efficient use in electronic devices. Compositional, o ptical, structural, defective and electrical properties have been inve stigated for both a-SiC:H films, having optical gap in the range 1.9-3 .25 eV, and a-SiN:H films, having optical gap in the range 1.9-5.2 eV. By Raman spectroscopy a lower structural disorder has been evidenced in a-SiC:H films compared to a-SiN:H ones and by electron spin resonan ce a lower spin density have been found in a-SiN:H films. The a-SiC:H and a-SiN:H films have similar electrical properties at the same band gap.