Growth mechanisms of III–V compounds by atomic hydrogen-assisted epitaxy

Epitaxial layers of InP and InGaAsP have been grown on (100) InP substrates by gas source molecular beam epitaxy while simultaneously exposed to an atomic hydrogen flux produced by a thermal cracker. Transmission electron microscopy and photoluminescence studies indicate improved structural and optical properties of the InGaAsP layers, while Hall effect measurements indicate no degradation in the electrical properties, as compared to layers grown by conventional epitaxy without hydrogen. This improvement is attributed to a reduction in lateral composition modulation (LCM), which develops at the surface of the InGaAsP layers during growth due to the existence of a miscibility gap. A detailed atomistic model, including surface reconstruction effects based on reflection high energy electron diffraction observations, is developed to explain the growth processes occurring on H-exposed (100) III–V surfaces. A simple rate equation model is used to understand the reduction in LCM in terms of a decreased surface diffusion length of adatoms in the presence of H.