<title>Photocurrent decay transient process in a Si1-xGex/Si superlattice</title>

Abstract

The photoelectric transient process of a 99 period Si<SUB>0.823</SUB>Ge<SUB>0.177</SUB>/Si superlattices (SL) was investigated by the photocurrent decay (PCD) method. Decay lifetimes of electron and hole in SL, Si cap and buffer layers are extracted from the transient intensity and polarity of the PCD signal. The temperature and bias dependences of lifetime exhibit the thermalization of heavy hole, the dissociation of free exciton, and the thermal activation of shallow impurity and dislocation. The thermalized hole jumps in and out of the well at low temperature and weak electric field, while it jumps or surfs over the well region by a strong electric field or at high temperature. The lifetimes of electron and hole are nearly the same in the Si cap layer, while the lifetime of hole is about one order of magnitude longer than that of electron in SL, possibly due to the quantum confinement of hole in the SL region.