Boron‐Doped Polycrystalline Si x Ge1 − x Films: Dopant Activation and Solid Solubility

Abstract

The solid solubility of B in is determined over the entire composition range from x = 1 (Si) to x = 0 (Ge). Polycrystalline films deposited using and were employed for the solubility study. Boron was introduced into the films either ex situ by ion‐implantation of or in situ by addition of to the gas mixture. The solubility results were obtained in the ion‐implanted films, and confirmed with the in situ doped ones. The solubility of B in Si is 8.1 × 1019 and at 800 and 900°C, respectively, in accordance with the results obtained in single crystal Si. The solubility of B in Ge is approximately at 800 or 900°C, in agreement with the reported value in the limited literature. The solubility of B in decreases with increasing Ge content, but does not follow a single exponential function that would link the solubility in Si and that in Ge. Furthermore, in situ doping is found superior to ion‐implantation because already at 500°C, low resistivity films are deposited with uniformly distributed high concentrations of electrically active B atoms exceeding the respective solubility limits.