Linewidth analysis of the photoluminescence from InAs/GaSb/InAs/AlSb type-II superlattices

Abstract

We present photoluminescent (PL) linewidth measurements on InAs:GaSb, type-II superlattices as a function of temperature and power. The observed PL linewidth for the samples, studied at 80 K, was 40–60 meV, which is significantly larger than a thermally broadened line of width 2 kT. The larger linewidth is well explained by a combination of homogeneous and inhomogeneous broadening. The data suggest that the inhomogeneous broadening is dominated by interface roughness and that the roughness amplitude at the InAs–GaSb interface is on the order of 1 ML. A significant fraction of the broadening can be accounted for by the presence of interfacial regions which show a 1 ML decrease in the GaSb layer thickness. To account for homogeneous broadening, a Lorentzian function of width δ (full width at half maximum) is employed to smooth and broaden the synthetic spectrum which is calculated from a simple model of the spontaneous emission rate. A δ=10 meV was found to give the best fit of the synthetic spectra to the observed spectra. The spectral distribution was also found to be dependent on excitation power, and the data indicate that the photogenerated carriers preferentially occupy and fill the low energy regions of the heterointerface.