Light emission from tensile-strained n-type epitaxial Ge thin films on Si by ultrahigh vacuum chemical vapor deposition

Recently, Ge has been intensively studied as a light emission material that emits at ~1.5 μm, as it has been theoretically proven to be a promising candidate to realize Si-based light source for on-chip and chip-to-chip communications. In this paper, photoluminescence (PL) is reported from heavily phosphorus (P)-implanted epitaxial Ge thin films on Si. Sheet resistance has been measured to characterize the dopant concentration in Ge. X-ray diffraction (XRD) and micro-Raman spectroscopy have been employed to investigate the Ge crystalline quality and film strain, which are both important factors of light emission efficiency of Ge epilayer on Si. Thermal annealing effect on dopant activation, tensile-strain, and PL has been investigated. It is found that the annealing temperature of 700°C gives the most effective dopant activation, in-plane tensile strain of 0.4%, and high crystalline quality, leading to strongest PL emission.