IMPROVEMENTS IN THE HETEROEPITAXIAL GROWTH OF GAAS ON SI BY MOVPE

We describe methods of improving the metalorganic vapour phase epitaxy (MOVPE) growth of heteroepitaxial GaAs on Si. The low temperature growth step at the start is optimized by using the new alternative group III precursor dimethyl-ethyl-amine-gallane (GaH3.N(CH3)(2)C2H5 (DMEAGa)) as a substitute for the conventional group III compound TMGa. Further improvements in surface morphology and X-ray diffraction linewidth are obtained by applying the modulated atomic layer epitaxy (ALE) for this growth step. Thermal cycle annealing which is much more effective in dislocation reduction than constant temperature annealing has been optimized with respect to the high as well as the low temperature steps. We present a model of low temperature behaviour of dislocations to explain the role of cooling the samples during thermal cycle annealing. An additional improvement of layer quality is achieved by introducing a thin (AlGa)As-layer after the low-temperature-GaAs-layer leading to a confinement of dislocations after performing thermal cycle annealing as established by TEM-investigations.