Study On Properties Of GaN-Based High Power LED Chip On Si Substrates

The development of light-emitting diodes (LEDs) has occurred over a period of over 60 years, beginning with the discovery of the first p-n junction blue GaN-based LED in 1989. The GaN-based LED is the linchpin of the LED market, it forms the key ingredient in green and blue emitters, as well as providing the foundation for white LEDs employing yellow phosphors. High power LED is suitable for high luminance applications like automotive headlights, large-area displays and general illumination. A new developed high power GaN-based LED has shown great advantages over traditional LED in the device performance. Yet, in the fabrication process of GaN-based LED, several processes still remain to be optimized.In this paper, we discussed some device properties of GaN-based LED on Si substrates including:reliabilities, junction temperature and the efficiency droop with current increase. Some results of this study were achieved as following:1. The electrical and optical aging characteristics of GaN-based light-emitting diodes on Si substrate have been studied. The LED samples were stressed at room temperature with an injection current of 200 mA. Light output increased in the first stage and decreased with aging time. Reverse current and forward current at low bias were increased significantly. The EQE attenuation before and after aging were significantly different at different injection currents. The smallest attenuation occurred at the current density range corresponding to the highest efficiency.2. The linear relationship between forward voltage and junction temperature was researched and could be applied to LED junction temperature measurements.3. The output power of blue and green LEDs were closely related to the working environment and driving conditions. The L-I curve changed from linear relationship to superlinear relationship with increasing temperature in the small current regime and changed from superlinear relationship to sublinear relationship under 300K temperature. The current density viz appearance of peak EQE i.e. efficiency droop monotonously decreased and the decline rate of EQE at 100K was fastest in high current density, both caused of carrier leakage. This work was supported by the National 863 nanometer project (No.2003AA302160) and electron development fund in China。Xiao Youpeng(Material physics and chemistry) Directed by Professor Jiang Fengyi...