Thermal characteristics of InGaN-based green micro-LEDs

We have investigated the thermal characteristics of InGaN-based green micro-light-emitting diodes (micro-LEDs) without the passivation layer in a wide junction temperature range of 298-453 K. The decreased temperature coefficient (dV(f)/dT) of the device with a smaller device size is attributed to the increased series resistances for the smaller devices, largely affected by the defects due to sidewall damage of the active layer. The ideality factor of 2.02 at 298 K suggests that the charge transport mechanism could be defect-assisted tunneling. In addition, it is observed that the ideality factor decreases with increasing temperature. The results of the C-V measurements suggest similar electron and hole concentrations in the depletion region, leading to a balanced electron-hole recombination in the active layer. It was also found that the temperature-dependent bandgaps of ternary In0.3Ga0.7N obtained from electroluminescence spectra of micro-LEDs agree with the calculated values by using the semi-empirical Varshni relationship.