Electroluminescence from metal-insulator-semiconductor tunneling diodes using compressively strained Ge on Si0.5Ge0.5 virtual substrates

Direct band gap optical transition in compressively strained Ge film is demonstrated for the first time under current injection through a metal-insulator-semiconductor diode structure. The compressively strained Ge layer is grown on the relaxed Si0.5Ge0.5 substrate by solid source molecular beam epitaxy. The electroluminescence of direct band gap emission from strained Ge film and TO phonon assisted transition in Si and SiGe from the virtual substrate is observed under different current injections. The signature of heavy hole and light hole splitting in valence band is observed in the electroluminescence spectra from strained Ge layer. The temperature dependent electroluminescence characteristics have been studied over a temperature range of 10-300 K. AC frequency modulation for the Ge direct band electroluminescence has been studied to improve the emission efficiency over the DC bias. (C) 2013 Optical Society of America