Optimization of luminescent properties with respect to crystal growth temperatures for SiGe single quantum wells grown by molecular beam epitaxy

Abstract

SiGe single quantum wells grown pseudomorphically by solid source molecular beam epitaxy on Si substrates were investigated by low-temperature photoluminescence measurements. The study was meant to correlate efficient radiative recombination of SiGe quantum well structures to crystal growth temperatures. As a model system, nominally 4-nm-thick quantum wells with a Ge concentration of 20% were used and the influence of growth temperatures on photon energy, on full width at half maximum, and on photoluminescence intensity was examined. At low growth temperatures (500 °C or less), only a deep broad luminescence band is observed while at higher temperatures a phonon-resolved, near-band-edge emission is predominant until it disappears completely at about 1000 °C. A systematic study of the photoluminescence characteristics over the entire range of crystal growth temperatures where luminescence is observable at all, is reported and a ‘‘growth window’’ for optimized photoluminescence features was determined.