Low temperature epitaxy of high-quality Ge buffer using plasma enhancement via UHV-CVD system for photonic device applications

Under low thermal budget, high-quality Ge buffers were grown using plasma enhanced chemical vapor deposition (PECVD) technique by a two-step method in a cold-wall ultra-high vacuum system. Low threading dislocation density on the order of 10(7) cm(-2) with root mean square roughness values of several nanometers was achieved. Photoluminescence and ellipsometry characterizations revealed that the material and optical characteristics are comparable to that of a Ge buffer grown using the conventional CVD method at high temperature. Moreover, growth comparison of an active group IV GeSn layer on Ge buffers that were grown using PECVD at low temperature and CVD at high temperature was carried out to further examine its material and optical properties for optoelectronic device applications. The results indicate GeSn films with similar material and optical properties were achived using both Ge buffers. This work provides a promising growth process for industry to deposit Ge under conditions compatible with complementary metal-oxide-semiconductor technology.