Carrier recombination mechanisms in nitride single quantum well light-emitting diodes revealed by photo- and electroluminescence

Abstract

Light emission of nitride single quantum well light-emitting diodes operating in the range from 395 to 440 nm, grown by metal-organic vapor phase epitaxy, was investigated by means of photoluminescence (PL) and electroluminescence (EL) spectroscopies as functions of temperature and current injection level. The indium content of the active layers was varied via the growth temperature, which ranged from 770 to 810 °C. It was found that samples with higher indium contents (grown at lower temperatures) exhibit larger luminescence full widths at half maximum (FWHMs) and higher EL intensities. The larger FWHM points to a larger amplitude of the potential profile fluctuations, which suggests that these fluctuations may be useful for the increase in the device output power. In agreement with this result, the performed examination by PL measurements shows large thermal stability of the luminescence intensity for the lowest growth temperature sample. On the other hand, a nontrivial dependence of thermal stability on growth temperature suggests the additional involvement of different nonradiative recombination center concentrations in the individual samples, for example, because of dissimilar substrate qualities.