Different transfer paths for thermally activated electrons and holes in self-organized Ge/Si(001) islands in a multilayer structure

We investigated the temperature dependence (10-250 K) of the photoluminesce nce (PL) emission spectrum of self-organized Ge/Si(001) islands in a multil ayer structure. With elevated temperature, we find that the thermally activ ated holes and electrons are gathered by the Ge islands in different ways. The holes drift from the wetting layer into the islands, while the electron s, confined in Si due to type-II band alignment, leak into the Ge islands b y the electrostatic interaction with the holes accumulated there. It result s in an increase of the integrated intensity of island-related PL at a cert ain temperature range and a reduction of the phonon energy in the phonon-as sisted PL of the islands by involving a type-I transition into a type-II tr ansition. (C) 2001 American Institute of Physics.