Effects of p-GaN Growth Temperature on a Green InGaN/GaN Multiple Quantum Well

The effects of growth temperature of a p-GaN top layer on the properties of green light-emitting diodes (LEDs) were investigated. The LED structures were grown on c-plane sapphire substrates by using metalorganic chemical vapor deposition. In order to enhance LED performance, we optimized the Hall mobility and the hole concentration by varying the growth temperature of the p-GaN layers. After the optimization, three InGaN/GaN multi-quantum well (MQW) LED structures with different p-GaN growth temperature (970, 1000, 1030 ℃) were fabricated. The photoluminescence (PL) peaks of the three LEDs were observed at 520, 503 and 502 nm, respectively. Although the LED with 1000 ℃ p-GaN revealed a peak wavelength similar to one with 1030 ℃ p-GaN, the former exhibited almost two times higher electroluminescence (EL) and PL intensity, than the latter. This was attributable to an enhancement of the internal quantum efficiency resulting from a better interface quality of the underlying InGaN/GaN MQW active layers and the improved electrical property of the p-GaN top layer. The PL and the EL intensity of the LED with 970 ℃ p-GaN was lower due to the increased non-radiative recombination at a high In composition.