Characterization of GaAs films grown on Si substrates by molecular beam epitaxy

Abstract

Because of several potential applications and advantages afforded by the heteroepitaxial GaAs-on-Silicon material system, several groups world-wide are attempting to grow device-quality GaAs on Si substrates.eg.1 Both metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) growth techniques have been widely utilized to achieve heteroepitaxial growth. However, certain fundamental materials and growth problems have thus far prevented any group from achieving heteroepitaxial GaAs of a quality similar to that obtainable from bulk GaAs crystals. A high density of threading dislocations, microtwins/stacking faults, antiphase domain boundaries (APBs) and microfissures can form under non-ideal conditions. These defects result, in part, from stresses generated due to the ∼4% lattice mismatch and the different coefficients of thermal expansion between GaAs and Si. 2 Ex-situ characterization of this materials system is essential to assess the material quality and to provide direction for future growth experiments. This contribution describes the TEM characterization methodology that we employ to analyze our GaAs grown on Si substrates by MBE.