Epitaxial Germanium thin films on Silicon (100) using two-step process

摘要

A two-step growth method for high-quality epitaxial germanium films on silicon (100) is presented. During the first step a seed layer of crystalline Ge is deposited on silicon. The seed layer is a 50-100 nm germanium thin-film crystallized by melting amorphous germanium deposited using PECVD. During the second step germanium is epitaxially deposited on top of the re-crystallized seed layer using LPCVD at 600°C. Scanning electron microscopy (SEM) reveal that the resulting germanium films are continuous, conformal and crack-free. X ray diffraction (XRD) pattern in the θ-2θ configuration shows a strong Bragg's peak corresponding to Ge (400). XRD rocking curve pattern in the vicinity of the Bragg peak for Ge(400) shows a sharp peak with a FWHM of only 512 arc sec, indicating highly-oriented Ge film. XRD phi-scan for (221), (111) and (110) planes of germanium show sharp peaks at 45° interval, proving the in-plane epitaxy of germanium which have a four-fold cubic symmetry. The epitaxial germanium films on silicon are useful for heterogeneous CMOS devices, photonics, IR photodetectors, and low-cost III-V photovoltaics.