Degradation of InGaN/AlGaN LED on sapphire substrate grown by MOCVD

We report an optical degradation of an InGaN/AlGaN double-heterostructure light-emitting diode (LED) on a sapphire substrate grown by metallorganic chemical vapor deposition. The InGaN/AlGaN LED exhibited an optical output power of 0.17 mW, external quantum efficiency of 0.2 %, and the peak emitting spectrum at 437 nm with full width at half-maximum of 63 nm under 30 mA dc operation at 300 K. The InGaN/AlGaN LED showed the optical degradation under high injected current density. Electroluminescence, electron-beam induced current and cathodoluminescence observations show that the degraded InGaN/AlGaN LED exhibits formation and propagation of dark spots and a crescent-shaped dark patch, which act as nonradiative recombination centers. The values of degradation rate under injected current density of 0.1 kA/cm² were determined to be 1.1 × 10^-3, 1.9 × 10^-3 and 3.9 × 10^-3 h^-1 at ambient temperatures of 30, 50 and 80°C, respectively. The activation energy of degradation was also determined to be 0.23 eV.