Epitaxial Ge thin film Growth on Si Using a Cost-Effective Process in Simplified CVD Reactor

Germanium on silicon has the potential to enable growth of high quality group IV semiconductors for the field of silicon photonics by being used as virtual buffers. In addition Ge layers can be used in the fabrication of passive components such as waveguides and resonators. A cost-effective technology for the heteroepitaxial growth of Ge on Si will be highly beneficial. In this work, a simplified chemical vapor deposition reactor was assembled in-house to deposit Ge films. Epitaxial Ge film growth on Si (100) substrates was accomplished without requiring ultra-high vacuum conditions or a high temperature substrate pre-deposition bake thereby minimizing the economic and thermal budget of the process. Films were deposited using digermane (Ge₂H₆) precursor in a single step at a process temperature of 350 °C and chamber pressures of 1-10 Torr. Films were achieved at high chamber background pressures (>10^-6 Torr) by implementing a thorough ex situ substrate cleaning process and optimizing times for wafer loading, chamber pumping and initiation of film deposition. Transmission electron microscopy and X-ray diffraction were used to confirm the epitaxial growth and crystalline quality of the obtained films. Optical properties of the films were characterized using Raman spectroscopy, Photoluminescence and Infra-red spectroscopy.