Influence of disorder on luminescence from pseudorandomized strained Si1-xGex/Si superlattices

Carrier localization in a disordered potential was studied in type-I strained Si1-xGex/Si superlattices (SLs) when layer widths have been artificially pseudorandomized. The photoluminescence (PL) intensity under a transverse bias voltage varies monotonically and exhibits a folded increase as the bias is increased as opposed to an ordered SL where only steady drop-off of PL intensity, symmetric with respect to bias polarity, was observed with increasing field strength. The results indicate that electron and hole wave functions are located spatially apart at zero bias due to disorder-induced localization. We point out that such a wave-function displacement is even pronounced for type-II SL potentials in the presence of monolayer thickness fluctuation. (C) 1996 American Institute of Physics.