Midwave infrared InAs/GaSb superlattice photodiode with a dopant-free p–n junction

Abstract

Midwave infrared (MWIR) InAs/GaSb superlattice (SL) photodiode with a dopant-free p–n junction was fabricated by molecular beam epitaxy on GaSb substrate. Depending on the thickness ratio between InAs and GaSb layers in the SL period, the residual background carriers of this adjustable material can be either n-type or p-type. Using this flexibility in residual doping of the SL material, the p–n junction of the device is made with different non-intentionally doped (nid) SL structures. The SL photodiode processed shows a cut-off wavelength at 4.65μm at 77K, residual carrier concentration equal to 1.75×1015cm−3, dark current density as low as 2.8×10−8A/cm2 at 50mV reverse bias and R0A product as high as 2×106Ωcm2. The results obtained demonstrate the possibility to fabricate a SL pin photodiode without intentional doping the pn junction.