Nucleation and Growth Processes in OMCVD of GaAs

Abstract

ABSTRACTThe initial stages of GaAs growth on mirror-polished metal (W, Mo), semiconductor (Si, GaAs), and insulator (alumina) substrates have been experimentally studied in the organometallic chemical vapor deposition (OMCVD) process. Growth on the metallic substrates is often polycrystalline and nonepitaxial, while epitaxial GaAs layers with preferred orientations can be grown relatively easily on the nonmetallic substrates. The rate of nucleation of GaAs on all the substrates is found to increase with increasing arsine flow rate and with decreasing growth temperature. Our experimental results suggest that the GaAs nucleation process on all the substrates consists of an initial condensation and nucleation of gallium and subsequent formation of GaAs by arsenic supersaturation. In addition, following the nucleation of GaAs, a decrease in the substrate temperature is observed until further GaAs nucleation occurs, suggesting continued supersaturation. The nonepitaxial growth on the metallic substrates is attributed to the high rate of GaAs nucleation on these substrates.