Acceleration of the yellow band luminescence in GaN layers via Si and Ge doping

A huge acceleration of the yellow band defect luminescence (YB) with increasing Si and Ge doping concentration in GaN layers has been observed and studied. The donor doping concentrations in the n-type GaN varied from 5 × 1016 cm−3 to 1.5 × 1019 cm−3 for undoped, Si-doped, and Ge-doped samples. Consequently, the fastest component of the photoluminescence (PL) decay time curve accelerated from 0.9 ms to 40.3 ns, and the mean decay time from 20 ms to 260 ns with increasing doping concentration. We have proposed an explanation based on a theoretical model of donor-acceptor pair transition (DAP) and electron-acceptor (e-A0) recombination at higher dopant concentrations, which is supported by several measurement techniques as room-temperature radioluminescence (RL), PL measurements or thermally stimulated luminescence (TSL). Last but not least, we have shown a change in the morphology of samples with the increasing dopant concentration, especially 3D columns formation with the high level of Si-doping and its influence on the light extraction from the GaN layer. The paper shows an uncommon way of dealing with slow unwanted YB, which detriment the GaN luminescence properties.