Temperature-dependent emission intensity and energy shift in InGaN/GaN multiple-quantum-well light-emitting diodes

Temperature-dependent electroluminescence (EL) of InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) has been investigated to illustrate the role of localization effects in carrier capture and recombination. The devices have identical structure but with varying indium content in the active region. A large redshift of the emission peak with decreasing temperature is observed in the UV and blue LEDs over the temperature range of 77-200 K, accompanying a pronounced decrease of EL intensity. This redshift reflects carrier relaxation into lower energy localized states and the change in carrier recombination dynamics at low temperatures. In contrast, the peak energy of the green LEDs exhibits a smaller temperature-induced shift, and the emission intensity increases monotonically with decreasing temperature down to 5 K. Based on a rate equation analysis, we find that the densities of the localized states in the green LEDs are more than two orders of magnitude higher than that in the UV LED. (C) 2003 American Institute of Physics.