Alloy-fluctuation-induced exciton localization in high-Mg-content (0.27 ≤ x ≤ 0.55) wurtzite MgxZn1-xO epilayers

Stokes shifts and near-band emission in high-Mg-content single-phase wurtzite Mg(x)Zn(1-x)O (0.27 <= x <= 0.55) epilayers were investigated by photoluminescence (PL) and photoluminescence excitation combining laser and synchrotron excitation experiments. The observed Stokes shifts (e.g. 365 meV for the sample containing 55% Mg) as well as the 'S-shaped' temperature dependence of the maximum PL emissions were explained in terms of Mg compositional fluctuations in our sample resulting in exciton localization in potential traps and, consequently, suppression of non-radiative recombination making high-Mg-content MgZnO a good candidate for optical applications.