Crystallization behavior of microcrystalline silicon germanium

• μc-Si1 − xGex:H thin films were prepared for the solar cell application.
• We examined the crystallization behavior of μc-Si1 − xGex:H films.
• μc-Si1 − xGex:H films showed acceptable electrical properties.
• Ge content in μc-Si1 − xGex:H should be optimized further for solar cell absorber.

Hydrogenated microcrystalline silicon germanium (μc-Si1 − xGex:H) thin films were evaluated as a bottom cell absorber for multi-junction solar cells based on Si thin films. The crystallization behavior of μc-Si1 − xGex:H was examined. Raman spectroscopy and grazing angle X-ray diffraction showed that the crystallinity of the μc-Si1 − xGex:H films decreased with increasing Ge content. Fourier transform infrared spectroscopy revealed an increase in the intensity of the GeH and GeH2 bonds in μc-Si1 − xGex:H due to the increased amorphous phase. The rapid GeH4 decomposition rate and preferential etching of Si bonds led to a decrease in crystallinity and an extremely high Ge content in the μc-Si1 − xGex:H films. The dark conductivity of μc-Si1 − xGex:H was affected by the internal crystallinity and an excessively high crystallinity deteriorated the electrical properties. The photo response increased from 102 to 103 with increasing Ge content. This study presents a comprehensive evaluation of the crystallization behavior of μc-Si1 − xGex:H films for solar cell absorber applications.