Plasma oxidation-enhanced composite passivation for surface leakage reduction in InGaAsSb extended SWIR photodetectors

We report a composite passivation scheme—O2 plasma pretreatment followed by dielectric deposition—to suppress surface leakage in extended short-wave infrared (e-SWIR) InGaAsSb photodetectors. The compositely passivated devices exhibit significantly enhanced surface resistivities of 1805 Ω cm (O2 plasma + SiO2) and 1793 Ω cm (O2 plasma + Si3N4), 2.2 and 1.4 times higher than devices passivated with SiO2 alone (820 Ω cm) and Si3N4 alone (1293 Ω cm), respectively. Gated device analysis combined with dark current modeling indicates that the performance enhancement originates from the modulation of surface potential by the composite passivation, which suppresses the two dominant surface leakage currents: generation–recombination current in the surface space-charge region and tunneling current due to hole accumulation. At the temperature of 300 K, the devices exhibit a 100% cutoff wavelength of 3.2 μm and a peak responsivity of 0.55 A/W at 2.2 μm. The dark current density is 1.2 × 10−2 A/cm2 at a bias of −0.05 V. The best performance is achieved with combined O2-plasma and Si3N4 passivation, yielding a peak specific detectivity of 7.7 × 109 Jones, which represents a 28.3% enhancement over the Si3N4-only device. These results confirm that the proposed composite passivation effectively suppresses surface leakage and enhances the performance of e-SWIR photodetectors. This approach shows promise for fabricating small-pixel infrared focal plane arrays capable of high-temperature operation.