Photoluminescence of HgTe Hg1-x Cdx Te superlattices and a study of minibands

It has been demonstrated that two closely spaced peaks in the infrared absorption spectra of several $\mathrm{Hg}\mathrm{Te}∕{\mathrm{Hg}}_{1\ensuremath{-}x}{\mathrm{Cd}}_{x}\mathrm{Te}(112)\mathrm{B}$ superlattices (SL's) are due to the $H1\text{\ensuremath{-}}E1$ intersubband transition at the center of the Brillouin zone and the zone boundary. The miniband width agrees well with $(8\ifmmode\times\else\texttimes\fi{}8\phantom{\rule{0.3em}{0ex}}\mathbit{k}∙\mathbit{p})$ calculations. The intersubband transition energies of SL's with both large and small miniband widths have been compared with photoluminescence (PL) spectra over a temperature range of $5\char21{}300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for a number of superlattices with band gaps between 100 and $510\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ at $5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The band gap as determined from the peak of the first derivative of the absorption coefficient, i.e., the corresponding intersubband transition energy, agrees well with the PL peak energy. With increasing temperature the PL peak energy increases faster than the band gap by a range of factors given by $0.25\char21{}0.75{k}_{B}T$, however, which are well within the width of the thermally broadened PL peaks.