Evidence of carrier localization in photoluminescence spectroscopy studies of mid-wavelength infrared InAs/InAs1-xSbx type-II superlattices

The temperature-dependent and excitation-dependent photoluminescence (PL) spectroscopy characterization of mid-wavelength infrared InAs/InAs1-xSbx type-II superlattices reveals evidence of carrier localization. Carrier localization is apparent in the 8 meV PL peak position blue shift from 4 K to 60 K while the peak full-width-at-half-maximum is non-monotonic, peaking at 25 K before increasing above 60 K. In addition, competition between two recombination processes is evident in the temperature dependent behavior of the PL peak integrated intensity under low excitation conditions: the intensity decreases from 4 K to 80 K, increases from 80 K to 160 K, and decreases above 160 K. Excitation dependent PL studies reveal the dominant recombination mechanism changes from free-to-bound or donor-acceptor-like recombination to excitonic or band-to-band recombination at similar to 60 K. These findings suggest that carrier localization is occurring below 60 K, and the confined carriers are holes as these are unintentionally doped n-type superlattices. The localization potentials are due to variations in the InAs1-xSbx, composition, the interfaces, and the InAs and InAs1-xSbx, layer widths. The width of a Gaussian distribution used to describe the density of states of the band tails due to carrier localization potentials ranges from 2 meV-4 meV. The larger energy corresponds to the smaller period superlattices, indicating the interface compositional variation is more prominent and creates larger localization potentials than in the longer period superlattices. Published by Elsevier B.V.