Study On The Reliability Of High-power GaN Based LEDs On Si Substrates

GaN-based LED is widely used in indoor lighting, lights, displays andautomotive industry, which has many features like energy-saving andenvironmentally friendly, high brightness, long life, and so on. In recent years, theGaN-based LED on silicon substrate, which has great value and developmentpotential, has received abroad widespread attention and research, and made a lot ofbreakthroughs. However, because of the application time is short, the reliability ofhigh-power LED devices is become one of people’s main concerns. Therefore, thepreparation, aging and temperature characteristics for green and white high-powerGaN-based LEDs on silicon substrate have been studied, and obtained the followingresults:1. Three groups of green high-power GaN-based LEDs on silicon substrate havebeen successfully prepared in the MOCVD system. Then, the aging characteristicswere investigated after accelerated aging for1000hours at500mA of current stress.The results show that the electrical properties and peak wavelength substantially isunchanged, and the optical power, luminous flux and relative EQE is slightly reduced.But after aging1000h, the optical power is reduced to97.5%of the initial valuebefore aging. The performance of three groups of green high-power GaN-based LEDson silicon substrate is stable at the high current aging. It shows that the growthprocess of high-power green GaN-based LED on silicon substrate has largertemperature window, and the reliability of the device can meets a variety ofapplications.2. Three types of high-power white GaN-based LEDs on silicon substrate havebeen successfully prepared by combination of high-power blue LEDs with yellowphosphor: direct coated phosphor potting LED, drip phosphor potting LED andcompletely phosphor potting LED. Then, the aging characteristics were investigatedafter accelerated aging for240hours at500mA of current stress. The results showthat after aging the color rendering index is slightly higher, but the luminous flux isdecreased. At the same time, the color temperature is substantially constant and theratio of the white color component in the spectrum is not changed much. It suggests that their optical performance is stable at the high current, and their reliability is good.3. The temperature characteristics of green and white high-power GaN-basedLEDs on silicon substrate has been studied from297K (room temperature) to447K.The results show that with the temperature increasing, both for green and the whiteLEDs, the reverse leakage current is increased, the voltage and luminous flux is dropt.Meanwhile, the peak wavelength become longer and the spectral is changed. Thecorrelation coefficient K for white LED’s voltage and temperature is-1.2mV/K. Withthe temperature increasing, in the white light spectrum, the proportion of blue lightfirst decreased and then increased, the proportion of yellow light first increased andthen decreased. Therefore, the parameters should be designed according to thepractical application during the package of the white LEDs.