Schematic representations of potential fluctuation and surface states caused by defects and band distortion. (a) Bulk GaN. (b) NP thoroughly depleted at low excitation power/low temperature. (c) NP with high carrier concentration at high excitation power/high temperature has a surface depletion region with small width. Arrows indicate recombination of free electrons and bound holes.
Slimane et al. Nanoscale Research Letters 2013 8:342 doi:10.1186/1556-276X-8-342