Growth of InP, GaAs, and In0.53Ga0.47As by chemical beam epitaxy

Abstract

A new epitaxial growth technique, chemical beam epitaxy (CBE), was demonstrated and investigated with the growth of InP and In0.53Ga0.47As GaAs. In this technique, all the sources were gaseous group III and group V alkyls. The In and Ga were derived by the pyrolysis at the heated substrate surface of either trimethylindium (TMIn) or triethylindium (TEIn), and trimethygallium (TMGa) or triethylgallium (TEGa), respectively. The As2 and P2 were obtained by thermal decomposition of triethylphosphine (TEP) and trimethylarsine (TMAs) in contact with heated Ta or Mo at 950–1200°C, respectively. Unlike conventional vapor phase epitaxy, in which the chemicals reached 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 very efficient use of the impinging chemicals and allowed the utilization of mechanical shutters. A similar gas handling system to that employed in conventional metalorganic chemical vapor deposition (MOCVD) 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 comparable optical quality to bulk substrates. Since TMIn and TEGa emerged as a single mixed beam, spatial composition uniformity was automatically achieved without the need of substrate rotation in the In0.53Ga0.47As epilayers grown. Lattice mismatch Δa/a≲4×10−4 was obtained.