Measurement of flicker noise as a diagnostic tool for hot-electron degradation in GaN-based leds

Hot-electron stressing on GaN-based light emitting diodes (LEDs) has been performed using a do stressing current. Detailed characterizations on the degradations in the optoelectronic and low-frequency noise properties of the devices have been conducted. Experimental results on I-V, electroluminescence (EL) and the integrated light output of the devices exhibit significant degradations with the stress time. Investigations on the low-frequency excess noise of the devices show that the degradations of the device properties arise from the generation of interface states at the In-GaN/GaN heterointerface due to hot-electron stressing. Over two orders of magnitude increase in the current noise power spectral density, S_I(f), is typically observed prior to the failure of the devices. Furthermore, it is shown that the initial rate of increase in S_I(f) resulting from a dc current stress time of 48 hours is strongly correlated to the lifetimes of the devices demonstrating that flicker noise measurement can be used as a diagnostic tool for hot-electron hardness of the device.