Impact of Be-doping on the material properties of InAs/InAsSb type-II superlattices for infrared detection

The material properties of p-type InAs/InAsSb superlattices are of interest for infrared photodiodes, but InAs/InAsSb superlattices are residually n-type and p-type superlattices have not been investigated thus far. This study examines the material properties of a mid-wavelength infrared InAs/InAsSb superlattice design doped with Be concentrations from 0.5-7x1016 cm-3. High-resolution x-ray diffraction revealed slight structural variation throughout the ~500 nm thick superlattice layer, but the RMS surface roughness was reasonable. Hall Effect measurements, taken at 10 K to remove any conduction effects from the undoped GaSb substrate, revealed the superlattice converting from ntype to p-type at Be:3x1016 cm-3. The maximum hole mobility achieved at the two highest Be doping levels was ~24,000 cm2/Vs, which is high for mid-wavelength infrared superlattices. The doped superlattices all had photoluminescence (PL) peaks 12 - 34 meV lower in energy than the undoped sample, and the PL peak FWHMs increased as the average superlattice mismatch increased, as expected. Comparing the photoresponse to the PL allowed the Be acceptor binding energy in the superlattice (13 meV) to be determined, which agreed with the reported Be acceptor binding energy in InAs.