As-grown Light-emitting Diodes Research Articles

InGaN light-emitting diodes with indium-tin-oxide photonic crystal current-spreading layer

Photonic crystal patterns on the indium tin oxide layer of an InGaN/GaN light-emitting diode are fabricated via nanosphere lithography in combination with dry etching. The silica spheres acting as an etch mask are self-assembled into a hexagonal closed-packed monolayer array. After etching, the photonic crystal (PhC) pattern is formed across the indium-tin-oxide (ITO) films so that the semiconductor layers are left intact and thus free of etch damages. Despite slight degradation to the electrical properties, the ITO-PhC light-emitting diodes (LEDs) exhibit enhancements of their optical emission power by as much as 64% over an as-grown LED. The optical performances and mechanisms of the photonic crystal LEDs are investigated with the aid of rigorous coupled wave analysis and finite-difference time-domain simulations.

Using the Taguchi method to improve the brightness of AlGaInP MQW LED by wet oxidation

To increase the external quantum efficiency of a light-emitting diode (LED) while limiting its forward voltage (Vf), we prepared both (AlxGa1-x)0.5In0.5 P LED and buried oxides through selective wet oxidation of the AlAs layers of AlAs-GaAs distributed Bragg reflectors. The wet oxidation process forms a stable AlxO material that acts as an insulation layer and affects both the carrier and optical confinements. To determine the tradeoff conditions for LED oxidation, we used the Taguchi method which is a robust technique that is often used to analyze significant trends that occur under a set of oxidation conditions. In this study, we used an L9 orthogonal array to measure the effects that a series of factors have upon the maximum brightness performance of the LED in an effort to limit the values of Vf. Relative to the as-grown LED, the oxidized LED that had been treated under the tradeoff wet-oxidation conditions displayed a sharply enhanced brightness (62.4% increase) in conjunction with only a slightly increased value of Vf (only a 24.5% increase)