Optical and electrical properties of polycrystalline silicon–germanium thin films prepared by aluminum-induced layer exchange

Abstract

Large-grained polycrystalline silicon–germanium (poly-Si1−xGex) thin films have been obtained by the aluminum-induced layer exchange (ALILE) process. The optical and electrical properties of these layers have been investigated as a function of the alloy composition. Optical reflection spectra and Hall effect mobility measurements indicate a high structural quality of the recrystallized thin films, which is comparable to bulk crystalline silicon–germanium (c-Si1−xGex) samples prepared by more sophisticated methods. Due to the increasing solubility of aluminum as a substitutional shallow acceptor with increasing germanium content, the room temperature carrier density of holes is found to increase from 1.5×1018cm−3 in poly-Si to 5×1020cm−3 in poly-Ge produced by ALILE.