Chemical beam epitaxy of InP and GaAs

A new epitaxial growth technique, chemical beam epitaxy (CBE), was demsonstrated and investigated with the growth of InP and GaAs. In this technique, all the sources were gaseous group III and group V alkyls. The In and Ga were derived by the pyrolysis of either trimethylindium or triethylindium and trimethylgallium or triethylgallium at the heated substrate surface, respectively. The As2 and P2 were obtained by thermal decomposition of triethylphosphine and trimethylarsine in contact with heated Ta or Mo at 950–1200 °C, respectively. Unlike conventional vapor phase epitaxy, in which the chemicals reach the substrate surface by diffusing through a stagnant carrier gas boundary layer above the substrate, the chemicals in CBE were admitted into a high vacuum growth chamber and impinged directly light of sight onto the heated substrate surface in the form of molecular beams. The beam nature of CBE resulted in efficient use of the impinging chemicals and allowed the utilization of mechanical shutters. A gas handling system similar to that employed in conventional metalorganic chemical vapor deposition with precision electronic mass flow controllers, was used for controlling the flow rates of the various gases admitted into the growth chamber. Growth rates as high as 3–5 μm/h have been achieved for both InP and GaAs. The InP and GaAs epilayers grown have smooth surfaces and an optical quality comparable to bulk substrates.