Structural characterization of solid phase crystallized Si0.5Ge0.5 films for photovoltaic applications

Intrinsic Si_0.5Ge_0.5 thin films were deposited on Si wafer substrates by RF sputtering in various substrate temperatures, film thickness and Ar (or Ar-H2) sputtering atmosphere for photovoltaic applications. The as-deposited films were annealed at different temperatures from 850°C to 1000°C. Effects of deposition parameter and annealing temperature on structural properties of the samples were studied by X-ray diffraction and Raman measurements. Thick sample (>1 ¿m) shows large crystallized grain size in low annealing temperature region (< 950°C), while thin sample (~600 nm) has a better crystallinity at high annealing temperature region (> 950°C). The samples deposited at 250°C exhibits improved grain size in high annealing temperature compared with the ones deposited at 100°C and 400°C. The introduction of H2 gas during sputtering can effectively improve the crystallization quality in low annealing temperature region, but have no obvious effect on high temperature annealing samples. Raman spectra reveal the Si-Si bond can only be well formed as well as Ge precipitation can be observed for high temperature annealing samples.