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.