Reliability study on green InGaN/GaN light emitting diodes

Although InGaN/GaN green light-emitting diodes (LEDs) are widely available, it is still challenging to grow green LED structures for emission at longer wavelengths due to the difficulty associated with the incorporation of In. The higher concentration of In may also affect the performance and reliability of the device. The reliability of green GaN LEDs with three different indium doping concentrations, with centre-wavelength of 520 nm, 540 nm and 550 nm, is studied in this paper. The electrical properties, including I-V characteristics, leakage current and 1/f noise were measured. The optical performance of the devices was also evaluated. The devices were subsequently subjected to a 1000 hours continuous stress test. The defect densities of the LED structures were also determined. Our results show that the 520 nm LED, which contains the lowest indium concentration in its quantum wells, produces highest optical output power at 20 mA. It also degrades slower than 540 nm and 550 nm LEDs.