Demonstration of Zn-diffused planar long-wavelength infrared photodetector based on type-II superlattice grown by MBE

We report on a planar long-wavelength infrared photodetector based on InAs/InAs1-xSbx type-II superlattice with zinc diffusion. The superlattice structures were grown by molecular beam epitaxy, followed by a post-growth Zinc diffusion process in a metal-organic chemical vapor deposition reactor. The planar photodetectors showed a peak responsivity of 2.18 A/W, under an applied bias of -20 mV, with a corresponding quantum efficiency of 44.5%, without any anti-reflection coating, and had a 100% cut-off wavelength of 8.5 μm at 77 K temperature. These photodetectors exhibit a specific peak detectivity of 3.0×1012 cm.Hz1/2/W, with a dark current density of 1.5×10-5 A/cm2 and the differential-resistance-area product of ~8.6×10-1 ω.cm2, under an applied bias of -20 mV at 77 K. A comparative study between the planar and conventional mesa-isolated photodetectors was also carried out.