Optical characterization of symmetric InAs/GaSb superlattices for detection in the 3-5 μm spectral region

Type-II InAs(N)/GaSb(N) superlattices (SLs) where the SL's period is composed by equal number N of InAs and GaSb monolayers (MLs) have been grown by solid source molecular beam epitaxy on n-type GaSb substrate. These SLs are made up of 100 periods with a number of MLs varying from N=5 to 15. Photoluminescence and photoresponse measurements, performed at 80 K, displayed peak positions and cut-off wavelengths between 3.8 and 8.3 μm. These results are in good agreement with a modified envelope function approximation model taking into account a strong perturbative potential at each InAs/GaSb interface. P-i-n photodetectors, made-up from strain-compensated InAs(10)/GaSb(10) undoped superlattice, showed a cut-off wavelength at 5.6 μm, an absorption coefficient value varying from 4×103 to 5.5×103 cm−1 in the 3-5 μm wavelength range, and a photovoltaic response up to 260 K.