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/cm 2 for the diodes passivated with SiO 2 and Si 3 N 4 and the unpassivated diode, respectively. The photodiode passivated with SiO 2 demonstrated a reduction in dark current density of approximately three times than that of the diode passivated with Si 3 N 4 . Therefore, the dynamic resistance-area product of the photodiode under the negative bias, passivated with SiO 2 , showed a larger value than that of the device passivated with Si 3 N 4 . In contrast, at 100–150 K, the resistance-area product at the zero-bias voltage of the photodiode passivated with Si 3 N 4 showed a higher value than that of the device passivated with SiO 2 . It is believed that the relatively low thermal stress between GaSb and Si 3 N 4 reduced the dark current density at zero bias and increased R 0 A in this temperature range.