Temperature dependent carrier localization in AlGaInN near-ultraviolet light-emitting diodes

We investigate the carrier localization effect in the low-indium ultraviolet AlGaInN light-emitting diodes with a 365 nm peak and a wide yellow luminous band over the visible range. Temperature-dependent electroluminescence spectra (EL) are measured under a wide range of temperature. We found that carrier localization effect relies on the carrier mobility and manifests itself by altering several macroscopic quantities, such as ELs and electrical resistance of the device. Under moderate injection densities, plots of EL peak energy vs. temperatures exhibits S-shapes. At low temperatures, line-width broadening in EL spectra and irregular humps in I-V curves were observed at similar level of injection densities. Both phenomena diminish as temperature increases and eventually disappear at room temperature. All the results stem from carrier localization and following delocalization effect. It suggests that the carrier mobility determine the degree of carrier localization effect - inactive carriers tend to be localized at low temperature but escape at high temperature from bindings of localization centers. As a result, carrier localization is intense only at low temperature for low-indium devices.