Luminescence properties of InGaN/GaN light-emitting diodes with violet, blue, and green emission

Abstract

The optical properties of InGaN/GaN light-emitting diodes (LEDs) grown at various temperatures were investigated using photoluminescence (PL) and time-resolved PL spectroscopies. The indium inhomogeneity generated localized states in InGaN/GaN quantum wells, and these affected the carrier dynamics. InGaN/GaN LED samples containing different indium contents were grown at temperatures of 900, 876, and 820 degrees C, resulting in violet, blue, and green emission, respectively. The violet LED sample exhibited the strongest PL intensity and the shortest PL decay time. This finding was attributed to an enhanced overlap of the electron and the hole wavefunctions, attributable to a reduced quantum-confined Stark effect due to the low indium contents in the violet LED. The PL decay times became longer with increasing emission wavelength, which can be explained by carrier transfer from weakly localized states to strongly localized states. These results indicate that the luminescence properties and the carrier dynamics of InGaN/GaN LEDs are affected by the growth temperature.