Dark current mechanisms in ultra-thin mid-wave infrared detectors

Mid-wave infrared photodetectors with ultra-thin (t<250nm) absorbers are characterized electrically and optically for a range of absorber doping concentrations. Negative differential resistance is observed in unintentionally doped absorber samples and is attributed to depletion of the ultra-thin absorber. A significant reduction in room temperature dark current of about 30% is observed in devices with compensation-doped absorbers when compared to those with unintentionally doped absorbers. A qualitative model of voltage-, temperature-, and doping-dependent dark current is developed and used to explain the diffusion-limited dark current of depleted-absorber detectors at high operating temperatures. The results presented offer insight into the electrical and optical behavior of ultra-thin mid-wave infrared detectors and potential approaches for further reduction in dark current.