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

本研究的目的是揭示原子氢辐照对GaAs分子束外延的影响，并将结果应用于选择性外延，即在GaAs衬底上选择性沉积，而在SiO_2或Si_3N_4覆盖的掩蔽区不沉积。预期效果如下。(1)各向异性横向生长速率的变化。(2)增强了Ga、Al和As原子的表面迁移。(3)对Ga、Al和As原子的吸附和解吸控制。(4)通过腐蚀氧化物进行表面清洗。首先，对各向异性横向生长进行了研究，得到了以下结果：在MBE生长的（001）GaAs上，GaAs和AlAl的横向生长速率存在较大的各向异性。随着衬底温度的升高或As_4压力的降低，沿[110]的生长速率增大。从这些结果和沿[1140]的GaAs横向生长速率的活化能值可以看出，沿[1140]的横向生长受到Ga和Al表面扩散的限制，而沿[110]的横向生长速率非常小。这种小生长速率的限制过程是Ga沿[110]和/或无活性Ga终止步骤的小扩散常数。得到的氢原子辐照效应如下。(1)实现了原子氢辐照对砷化镓衬底的低温清洗。在1500^ C钨丝的简易裂解槽中，通过氢气的解离提供了原子氢，螺旋电子能谱显示，在200^ C的温度下，原子氢辐照30分钟后，碳和氧分别在400^ C的温度下被去除。氢辐照后，砷化镓表面的RHEED模式由光晕变为条纹，证实了表面的清洁作用。(2)辐照原子氢使沿[001]的横向生长速率降低几个百分点。另一方面，原子氢辐照使[1140]沿线的速率降低到原来速率的- 30%。原子氢对砷化镓的腐蚀被认为是这一事实的起源。(3)通过在生长过程中辐照原子氢，将选择性生长温度降至580^ C。原子氢的诱导反应可能有助于降低选择性生长温度。少

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