SiO 2 /Al 2 O 3 double dielectric stack layer was deposited on the surface of the GaN-based Light-Emitting Diode (LED). The double dielectric stack layer enhances both the electrical characteristics and the optical output power of the LED because the first Al 2 O 3 layer plays a role of effectively passivating the p-GaN surface and the second lower index SiO 2 layer increases the critical angle of the light emitted from the LED surface. In addition, the effect of the Fresnel reflection is also responsible for the enhancement in output power of the double dielectric passivated LED. The leakage current of the LED passivated with Al 2 O 3 layer was -3.46 × 10 -11 A at -5 V, at least two and three orders lower in magnitude compared to that passivated with SiO 2 layer (-7.14 × 10 -9 A) and that of non-passivated LED (-1.9 × 10 -8 A), respectively, which indicates that the Al 2 O 3 layer is very effective in passivating the exposed GaN surface after dry etch and hence reduces nonradiative recombination as well as reabsorption of the emitted light near the etched surface.

Uniform spreading of injection current in light-emitting diodes (LEDs) is one of the crucial requirements for better device performances. It is reported that non-uniform current spreading leads to low output power, high current crowding, heating, and reliability degradation of the LED device. This paper reports on the effects of different surface and electrode geometries in the LEDs. To increase the output power of LEDs and reduce the series resistance, a rectangular-type LED (RT-LED) with a centered island cathode has been fabricated and investigated by comparison with a conventional LED (CV-LED). The performances of RT-LEDs were prominently enhanced via uniform current spreading and low current crowding. Performances in terms of increased output power and lower forward voltage of simulated RT-LEDs are much superior to those of CV-LEDs. Based on these results, we investigated the correlation between device geometries and optical characteristics through the fabricated CV and RT-LEDs. The measured output power and forward voltage of the RT-LEDs at 100 mA are 64.7% higher and 8% smaller compared with those of the CV-LEDs.