Electroluminescence properties of InGaN/GaN multiple quantum well-based LEDs with different indium contents and different well widths

Two InGaN/GaN multiple quantum well (MQW)-based blue light emitting diodes (LEDs) emitting photons at approximately the same wavelength, with different indium contents and well widths, are prepared, and the temperature-dependences of their electroluminescence (EL) spectra at different fixed injection currents are investigated. The results show that, compared with sample B with its lower indium content and larger well width, sample A with its higher indium content and smaller well width, has a stronger carrier localization effect and higher external quantum efficiency (EQE) at the lower fixed currents; however, upon increasing the injection current, both the localization effect and EQE for sample A decrease at a faster rate. The former is mainly attributed to the deeper potential levels due to the larger indium fluctuations originating from the higher indium content, and to the smaller well width-induced stronger carrier quantum-confine effect (QCE); the latter is mainly attributed to the more significant growing in the electron leakage and/or electron overflow originating from the smaller well width and larger lattice mismatch-induced stronger piezoelectric field, and to the more significant reduction in carrier localization effect originating from the smaller well width-induced smaller density of high-energy localized states.