Improvement of R0A product of type-II InAs/GaSb superlattice MWIR/LWIR photodiodes

The effects of atomic hydrogen and polyimide passivation on R0A product of type-II InAs/GaSb superlattice photo detectors for cut-off wavelength of both 6.5 μm and 12 μm were investigated. Low temperature current–voltage measurement shows that the use of atomic hydrogen during molecular beam epitaxy growth can improve R0A product by 260% for 6.5 μm cut-off superlattice diodes and by 50% for 12 μm cut-off ones. The R0A product of polyimide-passivated diodes with 12 μm cut-off is about 80% higher than those un-passivated ones. Wannier–Stark oscillations at higher reverse bias were observed for polyimide-passivated superlattice diodes with 12 μm cut-off. No Wannier–Stark oscillations were observed for un-passivated superlattice diodes, indicating that surface leakage current dominates in un-passivated diodes, while intrinsic dark current mechanisms such as tunneling and diffusion current dominate in polyimide-passivated diodes.