Influence of Growth Conditions and Surface Reaction Byproducts on GaN Grown via Metal Organic Molecular Beam Epitaxy:Toward an Understanding of Surface Reaction Chemistry

摘要

The surface reaction byproducts during the growth of GaN films via metal organic molecular beam epitaxy (MOMBE)were investigated as a means to optimize material properties.Ethylene and ethane were identified as the dom-inant surface reaction hydrocarbon byproducts,averaging 27.63percent and 7.15percent of the total gas content present during growth.Intense ultraviolet (UV)photo-excitation during growth was found to significantly increase the abundance of ethylene and ethane while reducing the presence of H_2 and N_2.At 920 deg C,UV excitation was shown to enhance growth rate and crystalline quality while reducing carbon incorporation.Over a limited growth condition range,a 4.5 X 10~(19)-3.4 X 10~(20)cm~(-3)variation in carbon incorporation was achieved at con-stant high vacuum.Coupled with growth rate gains,UV excitation yielded films with approx 58percent less integrated carbon content.Structural material property variations are reported for various ammonia flows and growth temperatures.The results suggest that high carbon incorporation can be achieved and regu-lated during MOMBE growth and that in-situ optimization through hydro-carbon analysis may provide further enhancement in the allowable carbon concentration range.