Experimental Research on Accelerated Life of GaN Based CBL-LED

Gallium nitride (GAN) based power light emitting diode (LED) has the advantages of energy saving, environmental protection, long life and so on. It has a wide range of application prospects in the fields of lighting and display. Although its performance has been improved in recent years and the products are becoming mature, the new LED structure will still bring new reliability problems. Therefore, it is of great significance to carry out photoelectric performance test and accelerated aging life test, and analyze its reliability and failure mechanism. In this paper, the initial photoelectric parameters of 1W GaN based blue LED with or without current blocking layer (CBL) are tested. The two kinds of LEDs are divided into four groups named A1, A2, B1 and B2 for accelerated life aging test. The devices selected by A1 and A2 are LED with CBL; the devices selected by B1 and B2 are LED without CBL. The accelerated life test of A1 and B1 devices is conducted at 700mA/25°C, and the accelerated life test of A2 and B2 devices is conducted at 900mA/25°C. During the experiment, the interval time of photoelectric parameter measurement is determined according to the actual situation of the experiment and the measurement of photoelectric parameters such as luminous flux, luminous efficiency and forward voltage, etc. is completed. The results showed that the luminous flux attenuation of the blue LED with CBL under 700mA and 900mA working current was 5% and 1.76% smaller than that of the blue LED without CBL structure. The LED with CBL structure has slower attenuation and better device performance. The forward voltage of the device increases with the increase of the aging time. The reason is that the ohmic contact resistance of the p-type layer increases due to the influence of large current and higher junction temperature, and the degradation of the packaging material also causes the series resistance to increase. Finally, the actual life of the device when it meets the L50 standard under normal current is deduced according to the inverse power law model. LEDs with or without CBL structure are 93555h and 40881h, respectively. LEDs with CBL structure have longer life and higher reliability.