The Effects of Atomic Hydrogen on Molecular Beam Epitaxy of GaAs and its Application to Selective Growth

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The target of this research is to reveal the effects of atomic hydrogen irradiation on the molecular beam epitaxy of GaAs and applying the results to the selective epitaxy, which means the selective deposition on the GaAs substrate and no deposition on the masked area covered by SiO_2 or Si_3N_4.The expected effects are as follows.(1) The change in the anisotropic lateral growth rate.(2) The enhancement of surface migration of Ga, Al and As atoms.(3) The control of the adsorption and desorption of Ga, Al and As atoms.(4) The surface cleaning by eching the oxide.Firstly, the anisotropic lateral growth is examined and the following results were obtained. There is large anisotropy in latera growth rate of GaAs and AlAl on (001) GaAs grown by MBE. With increasing the substrate temperature or decreasing As_4 pressure, the growth rate along [110] increases. From these results and the value of the activation energy of GaAs lateral growth rate along [1140], it is concluded that the lateral gro … More wth along [1140] is limited by surface diffusion of Ga and Al. On the other hand, the growth rate along [110] is very small. Thelimiting process of this small growth rate is the small diffusion constant of Ga along [110] and/or the inactive Ga terminated steps.The obtained effects of atomic hydrogen irradiation are as follows.(1) Low-temperature cleaning of GaAs substrate by atomic hydrogen irradiation was achieved. Atomic hydrogen was provides by dissociation of hydrogen gas, which was carried out in a simple cracking cell with a 1500^ﾟC tungsten filament, Auger electron spectroscopy showed that carbon was removed at 200^ﾟC and oxygen was removed at 400^ﾟC by 30-min atomic hydrogen irradiation. The surface cleaning of GaAs was confirmed by the change of RHEED pattern from halo to streak after the hydrogen irradiation.(2) The lateral growth rate along [001] is decreased by few percent by irradiating the atomic hydrogen. On the other hand the rate along [1140] is reduced to - 30 % of the original rate by the atomic hydrogen irradiation. The eching of GaAs by the atomic hydrogen is considered as the origin of this fact.(3) The temperature of the selective growth was lowered to 580^ﾟC by irradiating the atomic hydrogen during the growth. The eching reaction by atomic hydogen may contribute to the lowering of the selective-growth temperature. Less