ABSTRACT
This chapter compares Ge/GaAs(100) structures with similar structures incorporating a thin AlAs interlayer. The lattice-matched GaAs-Ge interface is not only important for the study of polar-nonpolar heteroepitaxy, but it may also prove useful for improving optical and electronic devices such as heterojunction bipolar transistors, metal-insulator-semiconductor field effect transistors (MISFET) and photodetectors. Outdiffusion of Ga, Al and As into epitaxial Ge grown on the AlAs inter-layer at initial growth temperatures of 200 and 300° C was investigated by Secondary ion mass spectroscopy (SIMS). Significant amount of Ga outdiffusion is observed by SIMS in a Ge/GaAs layer initiated at 300 °C. One possible application of the Ge/GaAs system is the complementary MISFET. Due to the small band gap of Ge, Ge substrates conduct at room temperature and unsuitable for field effect transistors (FET) applications due to leakage current and parasitic capacitance which degrade the high frequency performance.
