Luminescence of InGaN/GaN multiple quantum wells grown by mass-transport

We present an optical study of an In0.12Ga0.88N/GaN structure containing three quantum wells (QW) grown by metalorganic vapor phase epitaxy using mass transport. The mass-transport regions demonstrate a high structural quality with a threading dislocation density less than 10(7) cm(-2). The photoluminescence (PL) spectrum is dominated by a 40 meV - narrow line centered at 2.97 eV at 2 K. This emission has a typical PL decay time about 5 ns at 2 K within the PL contour. An additional line with longer decay time (about 200 ns) is observed at an energy of similar to2.85 eV. The position of this line shifts towards higher energies with increasing excitation power. The data are explained in terms of a model, where the PL originates from two nonequivalent quantum wells, which could be realized due to a potential gradient across the layers.