Similarity of the 3.42 eV and near-band-edge 3.47 eV luminescence bands in GaN

We demonstrate that the 3.42 eV photoluminescence (PL) band in GaN is of the same intrinsic origin as the near-edge $\sim$3.47 eV band, but arises from regions of inversed polarity characterized by different strain and growth rate. Two absorption edges are thermally detected at 0.35 K in nanocolumn structures, exhibiting both bands. Micro-PL studies have shown similar temperature/power behavior of these bands, with a competition in intensity in closely spaced spots accompanied by alterations of exciton level ordering. Strain-induced one-dimensional carrier confinement in small inversion domains likely explains the discrete narrow lines observed between the bands.