Direct gap photoluminescence of n-type tensile-strained Ge-on-Si

Room temperature direct gap photoluminescence (PL) was observed from n-type tensile-strained epitaxial Ge-on-Si. The PL intensity increases with n-type doping due to a higher electron population in the direct Gamma valley as a result of increased Fermi level. The direct gap emission also increases with temperature due to thermal excitation of electrons into the direct Gamma valley, exhibiting robustness to heating effects. These unique properties of direct gap emission in an indirect gap material agree with our theoretical model and make Ge a promising light emitting material in 1550 nm communication band. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3170870]