Optical properties of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>δ</mml:mi></mml:math>-doped ZnSe:Te grown by molecular beam epitaxy: The role of tellurium

Abstract

We have studied the optical properties of the $\ensuremath{\delta}$-doped ZnSe:Te system using photoluminescence (PL) and x-ray and Raman scattering. Two different types of sample were investigated, (1) with a single $\ensuremath{\delta}$ layer and (2) with three adjacent $\ensuremath{\delta}$ layers separated by undoped layers. All of these samples are of reasonable crystalline quality and have the symmetry of the host ZnSe lattice as determined by x-ray and Raman scattering. The PL from each sample is very similar to the PL from bulk Zn-Se-Te solutions at low Te concentrations. The PL from the single-$\ensuremath{\delta}$-doped material shows emission relatively close to the band edge which we attribute partly to ${\mathrm{Te}}_{2}$ clusters (nearest-neighbor pairs) and partly to non-nearest pairs. This PL changes with storage time, from which we conclude that the nearest-neighbor pairs are more stable than non-nearest-neighbor pairs. The triple-$\ensuremath{\delta}$-doped material also shows a deeper PL feature, with a peak at about 2.48 eV, which we attribute to ${\mathrm{Te}}_{n&gt;~3}$ clusters as well as to corresponding non-nearest-neighbors pairs.