PHOTOGENERATION AND TRANSPORT OF CARRIERS IN STRAINED SI1-XGEX/SI QUANTUM-WELL STRUCTURES

Generation and transport of carriers in strained Si1-xGex/Si quantum well structures were investigated by photoluminescence measurement with varying temperature and excitation power. It was found that the majority of carriers giving luminescence were produced inside the substrate beyond 1 mum and subsequently transported to the quantum wells on the surface side when a visible wavelength excitation source was used. Consequently, the emission of the quantum well closest to the substrate dominated the spectrum under a low excitation condition. In contrast, the emissions of the quantum wells on the surface side were observed at higher temperatures or under intense photopump. The evolution of surface-side quantum well emission is interpreted in terms of carrier escape out of the substrate-side quantum well in the form of either thermal jump to the barrier band-edge or overflow due to population saturation.