Photoluminescence determination of the Fermi energy in heavily doped strained Si1−xGex layers

Abstract
Photoluminescence (PL) measurements of strained Si1−xGex heavily doped p‐type layers with different Ge fraction x are reported in this letter. UHV chemical‐vapor‐deposition‐grown samples with x=0.08, 0.12, and 0.16 and doped with 4×1018 cm−3 boron atoms are studied. No‐phonon and TO‐phonon replicas corresponding to free‐electron band‐to‐band transitions are observed. Values of the band‐gap narrowing and Fermi level EF are determined from the PL curves. The earlier theoretical predictions that EF should increase (because of the decrease of the effective density of states) with increasing Ge fraction, are confirmed by PL experiments.