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

Large-grained polycrystalline silicon-germanium (poly- Si1-x Gex) 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-x Gex) 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× 1018 cm-3 in poly- Si to 5× 1020 cm-3 in poly- Ge produced by ALILE.