Temperature dependence of InGaP, InAlP, and AlGaP growth in metalorganic molecular-beam epitaxy

Abstract

Abstract Metalorganic molecular-beam epitaxy of InGaP, InAlP, and AlGaP was investigated at various temperatures (290–650°C), using triethylindium (TEIn), triethylgallium (TEGa), triethylaluminum (TEAl), and phosphine. Three distinct stages were observed in the temperature dependence of growth rate and epilayer composition of those ternaries. At lower temperatures below 390°C the incomplete pyrolysis of TEGa and TEAl limits the growth, while TEIn decomposes perfectly as low as 290°C. TEAl decomposition is incomplete at all the temperatures studied, and is enhanced by the existence of TEIn or TEGa. To explain this observation, a co-decomposition mechanism was proposed, in which thermal energy produced by the pyrolysis of TEIn or TEGa induces the decomposition of TEAl; complexes such as TEAl-TEIn and TEAl-TEGa are assumed to be formed by mixing the metalorganics in the vapor phase. In the moderate-temperature region of 390–520°C, the growth is limited by the supply of metalorganics. At higher temperatures above 520°C phosphorus evaporates from the superficial part of epilayers with breaking bonds of In-P, resulting in many indium droplets on the epilayer surfaces. The incorporation of gallium and aluminum atoms into the indium droplets reduces the growth rate of the GaP and AlP constituents in InGaP and InAlP epitaxy. By the absence of In-P bonds, the growth rate of AlGaP does not decrease up to 650°C, and no droplets are formed on the surfaces.