Study of Medium-Range Order and Defects in Hydrogenated Protocrystalline Silicon Films Deposited by Radio Frequency Plasma Enhanced Chemical Vapor Deposition

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Protocrystalline silicon films were deposited by RF plasma-enhanced chemical vapor deposition (PECVD) at a high deposition rate while varying deposition power. The short-range order (SRO) and medium-range order (MRO) of these films were thoroughly investigated using Raman spectroscopy. It was observed that the degrees of both SRO and MRO vary considerably for samples deposited under different powers, and improved SRO and MRO values are obtained in low-power-deposited films. From high-resolution transmission electron micrographs, it was clearly observed that for low-power-deposited films, a more highly ordered silicon matrix is obtained, which also shows a better MRO value. The microstructure factor was low for all the films, as observed from their FTIR spectra. The defect density of the protocrystalline silicon films were studied by electron spin resonance (ESR) spectroscopy and photothermal deflection spectroscopy (PDS), and it was observed that the films deposited at a higher power have a higher defect density and a higher subgap absorption level than the low-power-deposited films.
2007-11-15