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7 May 2019 ALD-Al2O3 passivation effects on surface characteristics of InAs/GaSb type-II superlattice infrared photodetectors
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To suppress the surface leakage current of InAs/GaSb Type-II superlattice (T2SL) infrared photodetectors, atomic layer deposited (ALD)-Al2O3 passivation effects have been investigated. By using the ALD-Al2O3 passivation layers, surface leakage current was more effectively suppressed than by using chemical vapor deposited-SiO2 passivation layers. The deposition temperature of ALD Al2O3 played an important role in minimizing the surface leakage current of T2SL infrared photodetectors. We found that the dark current density of mid-wavelength (MW) p-i-n structures was limited by their bulk components with Al2O3 passivation layers deposited at or below 200 °C, while the dark current density increased with the surface leakage when the layers were deposited at 260 °C. From the capacitance–voltage analysis, it was found that the deposition at 260 °C led to a large interface trap density at the Al2O3/GaSb interface. The results of X-ray photoelectron (XPS) spectroscopy show that the spectra of Sb2O3 decreases while that of Ga2O3 increases when the deposition temperature increases from 200 to 260 °C. This indicates that the reaction of Sb2O3 with GaSb is thermally enhanced. Based on these results, we conclude that Ga2O3 and/or elemental Sb may lead to an additional leakage path. Hence, suppression of the thermal decomposition of Sb-related oxides during Al2O3 deposition is required to obtain good passivation effects.
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R. Suzuki, K. Ozaki, K. Tsunoda, and H. Nishino "ALD-Al2O3 passivation effects on surface characteristics of InAs/GaSb type-II superlattice infrared photodetectors", Proc. SPIE 11002, Infrared Technology and Applications XLV, 110020B (7 May 2019);

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