MBE growth of mid-wavelength type II InAs/InAsSb superlattice photodetectors with wet etching and Al2O3 passivation

We systematically investigated the molecular beam epitaxy (MBE) growth of nBn mid-wavelength photodetectors based on type II InAs/InAsSb superlattice (T2SL) with a lattice-matched high bandgap AlAsSb layer as a barrier. A comprehensive set of structural and optical characterizations was performed using AFM, XRD, TEM, and FTIR spectrometry on the MWIR Ga-free InAs/InAsSb T2SLs. Temperature-dependent photoluminescence (PL) measurements verify the suitability of the designed T2SL for MWIR applications by meeting the mid-wave wavelength requirements and exhibiting a lower Varshni parameter α. Optimization of the wet etching process using a solution of H3PO4, C6H8O7, H2O2, and H2O significantly reduced surface roughness. Dark current measurements demonstrated a notable reduction from 1.13 × 10-4 A/cm2 to 7.47 × 10-7 A/cm2 at −0.5 V and 80 K for devices processed with the optimized etching process and Al2O3 passivation. Significantly, the 50% cut-off wavelength closely aligned with the PL peak at 5.07 μm, underscoring the suitability of MBE-grown InAs/InAsSb T2SLs for MWIR photodetector fabrication.