Direct band gap optical emission from compressively strained Ge films grown on relaxed Si0.5Ge0.5 substrate

Compressively strained Ge films have been grown on relaxed Si0.5Ge0.5 virtual substrate in ultra high vacuum using molecular beam epitaxy. Structural characterization has shown that the Ge films are compressively strained with partial strain relaxation in a film thicker than 3.0 nm, due to onset of island nucleation. Photoluminescence spectra exhibit the splitting of degenerate Ge valence band into heavy hole and light hole bands with a broad direct band gap emission peak around 0.81 eV. Temperature and excitation power dependent emission characteristics have been studied to investigate the mechanism of luminescence quenching at high temperatures and the role of non-radiative recombination centers. (C) 2013 AIP Publishing LLC.