Current-voltage characteristic of InAs/GaSb superlattice mid-infrared photodiodes

InAs(8ML)/GaSb(8ML) superlattice with p-i-n structure was grown on GaSb substrates by molecular beam epitaxy. IV characteristic under (NH4)2S passivation showed that the ideality factor was near 2 at lower forward bias where recombination current dominated and the factor was near 1 beyond 0.14 V where diffusion current dominated. A large number of combination centers appeared at the surface barrier region originated from the vacancy defects. Compared with (NH4)2S solution treatment, the surface leakage currents density after anode sulfide treatment decreased three orders of magnitude and the zero-bias resistance R0 was measured up to 106 ohms. The figure of merit R0A was up to 103cm-2.