Low temperature RF-PECVD epitaxy of thin film germanium layers on c-Ge and c-Si wafers

We report germanium epitaxial growth using standard radio-frequency plasma enhanced chemical vapor deposition (RF-PECVD) at 200°C. Spectroscopic ellipsometry and transmission electron microscopy (TEM) are used for layers characterization. High crystalline quality epitaxial germanium (epi-Ge) on (100) c-Ge wafers is obtained with this low temperature process. Despite 4.2% lattice mismatch, germanium crystal growth is also achieved on (100) c-Si substrate. Interestingly, defects rising from Ge/Si interface are mostly located within the first tens of nanometers, and epitaxial quality improves with thickness as shown by TEM analysis and surface threading dislocation density. Moreover, misfit stress is released very fast in this material, and Moiré pattern analysis reveals residual strain in the range of 0.4%.