Preferential growth of μc-Ge : H along the crystallographic axes of Si and Ge substrates by ECR plasma CVD

Abstract

Hydrogenated microcrystalline germanium (μc-Ge : H) films have been grown on crystalline (c-) Si and Ge substrates in a temperature range from 25 to 313 °C, by means of electron-cyclotron-resonance plasma chemical vapor deposition. An increase in substrate temperature induced an amorphous to microcrystalline phase transition at around 50 °C, and increased the crystalline volume fraction of μc-Ge : H on both c-Si and c-Ge. A volume fraction of nearly 100% was realized at 200 °C. Above this, (1 0 0) preferential growth of μc-Ge : H was observed on both c-Si(1 0 0) and c-Ge(1 0 0). For c-Si(1 1 1) and c-Ge(1 1 1) substrates, the growth direction was mainly (1 1 1), but containing (1 1 0) and (3 1 1) components, attributed to twin formation. The dependence of the film-surface roughness on the substrate temperature was also examined. The peak energy and magnitude of the photoluminescence decreased with increasing substrate temperature.