Radiationless recombination mechanisms in GaN surface layers determined from photoluminescence

Abstract

A peculiarity has been observed in the experimental dependence of the edge photoluminescence intensity (Φ) of GaN(0001) grown by HVPE on excitation (I). The peculiarity is a strong superlinearity at low excitation levels, namely, a superquadratic dependence. At high excitation levels the dependence is close to a linear one. A model has been proposed explaining the observed superquadratic dependence. According to this model the absorption of the exciting light takes place in the collection region of minority charge carriers. Therefore, a known approach can be used, which gives a description of the superquadratic dependence of luminescence intensity from a p-n junction on forward current. An analytic superquadratic dependence was obtained with the use of a model, assuming that the radiationless channel is provided via tunneling by the way of multiple hops along dislocations traversing the space-charge region, the dislocation in question having the form of a chain of localization centers. A power law experimental dependence of the luminescence intensity on excitation was observed.