Electrophysical characteristics of LEDs based on GaN epitaxial films

Forward and reverse current-voltage (I-V) characteristics of light emitting diodes based on GaN epitaxial films were investigated by differential spectroscopy. This technique is based on calculating the differential slope of the I-V curve on the log-log scale in the following form: alpha = d lg i/d lg V and gamma = d lg alpha/d lg V. The main peculiarity of reverse I-V curves is the absence of rectification. The I(V) dependence can be approximated as i varies approximately as V exp 3 at a low bias and i varies approximately as V exp 4 at high bias. These functions correspond to a high and superhigh level of double injection of current carriers, respectively. The forward current depends on voltage exponentially, with the ideality factor ranging from 6 to 8 under a bias of up to 1.5 V. The alpha(V) dependence has two maxima corresponding to a change of the charge flow mechanism from carrier diffusion to the field mechanism in the first case and to overcoming the recombination barrier in the second case. The second maximum is followed by light emission. The behavior of the I-V curves in the temperature range from 150-400 K is discussed and compared with that of spectral, kinetic, and power-current characteristics measured in the same temperature range. (Author)