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 metalorganic 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 density of 0.1 kA/cm(2) were determined to be 1.1x10(-3), 1.9x10(-3) and 3.9x10(-3) temperatures of 30, 50 and 80 degrees C, respectively. The activation energy of degradation was also determined to be 0.23 eV.