Passivation Study of InAs/GaSb Type-II Strained Layer Superlattice in Mid-wave Infrared Photodetector

This paper reports the results of a passivation study of InAs/GaSb type-II strained layer superlattice for a mid-wave infrared detector with p-on-n polarity. The cutoff wavelength of the fabricated photodiode was observed to be 5.5 µm at 77 K. At a negative bias of 0.1 V, the dark current density was measured to be 2.8 × 10−5, 8.2 × 10−5, and 3.1 × 10−2 A/cm2 for the diodes passivated with SiO2 and Si3N4 and the unpassivated diode, respectively. The photodiode passivated with SiO2 demonstrated a reduction in dark current density of approximately three times than that of the diode passivated with Si3N4. Therefore, the dynamic resistance-area product of the photodiode under the negative bias, passivated with SiO2, showed a larger value than that of the device passivated with Si3N4. In contrast, at 100–150 K, the resistance-area product at the zero-bias voltage of the photodiode passivated with Si3N4 showed a higher value than that of the device passivated with SiO2. It is believed that the relatively low thermal stress between GaSb and Si3N4 reduced the dark current density at zero bias and increased R0A in this temperature range.