Accumulation of holes at the mesa sidewall surface of InGaAsSb extended-short wavelength infrared photodetectors

This work investigates leakage mechanisms in InGaAsSb e-SWIR detectors by examining the surface states of the mesa sidewall and the longevity of passivation layers. The passivation efficacy of SU8, SiO₂ and S-SiO₂ films is evaluated, using an un-passivated photodetector as a reference. The S-SiO₂ composite film passivated InGaAsSb mesa sidewall exhibits the highest surface resistivity. To investigate the factors contributing to this high surface resistivity, we employed gate-controlled photodetectors. Our findings indicate that the neutralization of dangling bonds at the InGaAsSb surface by sulfide is not the main factor. Instead, by examining the longevity of these passivation films, we determined that the high resistivity of the S-SiO₂ film is related to its airtightness. Additionally, the GCPD results indicate an accumulation of holes at the InGaAsSb surface. These findings suggest that a pBp structure may provide advantages in reducing the leakage current of InGaAsSb e-SWIR photodetectors.