CAPTURE, STORAGE, AND EMISSION OF HOLES IN SI SI1-XGEX/SI QWS FOR THEDETERMINATION OF THE VALENCE-BAND OFFSET BY DLTS/

We report on the problem of the determination of the valence band offs et between strained Si1-xGex and unstrained Si layers by deep level tr ansient spectroscopy (DLTS) on Si/Si1-xGex/Si quantum well (QW) struct ures. To observe a DLTS signal, the holes must be stored long enough ( >1ms) in the QW so that the thermal emission is the dominating process . We achieved sufficiently long storage times by using two different s tructures. The first one was obtained by selective growth which leads to a lateral limitation of the QW-layer, where the holes are localized . For the second ones, the localization of holes is due to the presenc e of Si1-xGex-islands.