Optical characterization and metal–nonmetal transition of boron-doped Si1−xGex alloy

Abstract

We report measurements of the optical band gap of Si1−xGex, by photoacoustic spectroscopy technique. The material has been obtained by a mechanical alloying process. Due to its technological application, in high-performance bipolar transistors and integrated circuits, the interest in the physical properties of Si1−xGex has recently increased. The metal–nonmetal transition (for x=0.2) is determined to be 3.2×1018 cm−3. The optical band gap estimated from the absorption data at high boron concentration shows band gap narrowing when compared to the undoped alloy.