Thermal instability of GaSb surface oxide

K. Tsunoda, Y. Matsukura, Ryo Suzuki, M. Aoki
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引用次数: 5

Abstract

In the development of InAs/GaSb Type-II superlattice (T2SL) infrared photodetectors, the surface leakage current at the mesa sidewall must be suppressed. To achieve this requirement, both the surface treatment and the passivation layer are key technologies. As a starting point to design these processes, we investigated the GaSb oxide in terms of its growth and thermal stability. We found that the formation of GaSb oxide was very different from those of GaAs. Both Ga and Sb are oxidized at the surface of GaSb. In contrast, only Ga is oxidized and As is barely oxidized in the case of GaAs. Interestingly, the GaSb oxide can be formed even in DI water, which results in a very thick oxide film over 40 nm after 120 minutes. To examine the thermal stability, the GaSb native oxide was annealed in a vacuum and analyzed by XPS and Raman spectroscopy. These analyses suggest that SbOx in the GaSb native oxide will be reduced to metallic Sb above 300°C. To directly evaluate the effect of oxide instability on the device performance, a T2SL p-i-n photodetector was fabricated that has a cutoff wavelength of about 4 μm at 80 K. As a result, the surface leakage component was increased by the post annealing at 325°C. On the basis of these results, it is possible to speculate that a part of GaSb oxide on the sidewall surface will be reduced to metallic Sb, which acts as an origin of additional leakage current path.
GaSb表面氧化物的热不稳定性
在开发InAs/GaSb型超晶格(T2SL)红外探测器时,必须抑制台面侧壁的表面漏电流。为了达到这一要求,表面处理和钝化层都是关键技术。作为设计这些工艺的起点,我们研究了GaSb氧化物的生长和热稳定性。我们发现,GaSb氧化物的形成与GaAs的形成有很大的不同。Ga和Sb都在GaSb表面被氧化。相反,在GaAs中,只有Ga被氧化,As几乎没有被氧化。有趣的是,GaSb氧化物即使在去离子水中也能形成,在120分钟后形成一层厚度超过40纳米的非常厚的氧化膜。为了检验GaSb天然氧化物的热稳定性,在真空中对其进行了退火,并用XPS和拉曼光谱对其进行了分析。这些分析表明,在300°C以上,GaSb原生氧化物中的SbOx将被还原为金属Sb。为了直接评估氧化物不稳定性对器件性能的影响,制作了一个在80 K时截止波长约为4 μm的T2SL p-i-n光电探测器。结果表明,经325℃后退火后,表面泄漏成分增加。根据这些结果,可以推测,侧壁表面的一部分GaSb氧化物将被还原为金属Sb,这是额外泄漏电流路径的来源。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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