Time-resolved electroluminescence of bulk Ge at room temperature

Time-resolved spectroscopy of bulk Ge at room temperature allows to differentiate direct-gap electroluminescence (EL) from indirect-gap EL. The results indicate that there exists strong coupling between the eight-fold indirect L-valleys and the zone-center Γ-valley due to intervalley phonon scattering at room temperature in the absence of built-in strain. Pulse modulation of EL at 10-MHz is consistent with the relevance of the direct-gap transition.