Limiting factors of GaN-on-GaN LED

GaN-on-GaN light emitting diodes (LEDs) have been considered to present the path towards ultimate LED technology. However, at present, the performance of the LEDs is still lower in comparison to GaN-on-sapphire LEDs. This work attempted to identify the possible factors that limit the performance of a GaN-on-GaN LED. To perceive this clearly, a GaN-on-patterned sapphire substrate (PSS) LED was also included in this study for comparison. It was found that the GaN-on-GaN LED exhibited lower performance (e.g. external quantum efficiency) than the GaN-on-PSS LED, especially at higher currents, despite its dislocation density being much lower than the latter. This is because the GaN-on-GaN LED had a lack of V-pits formation and carriers localization. As a result, the LED showed higher operating voltage and lower radiative recombination in comparison to the GaN-on-PSS LED.