Eun-jeong Kang

Improved light-output and electrical performance of InGaN-based light-emitting diode by microroughening of the p-GaN surface

We report on an InGaN-based light-emitting diode (LED) with a top p-GaN surface microroughened using the metal clusters as a wet etching mask. The light-output power for a LED chip with microroughening was increased compared to that for a LED chip without one. This indicates that the scattering of photons emitted in the active layer was much enhanced at the microroughened top p-GaN surface of a LED due to the angular randomization of photons inside the LED structure, resulting in an increase in the probability of escaping from the LED structure. By employing the top surface microroughened in a LED structure, the power conversion efficiency was increased by 62%.

Improvement in Light-Output Power of InGaN/GaN LED by Formation of Nanosize Cavities on p-GaN Surface

To improve the extraction efficiency of InGaN/GaN multiple quantum well light-emitting diodes LEDs , nanosize cavities werefabricated on a top p-GaN surface by inductively coupled plasma etching utilizing self-assembled platinum clusters as an etchmask. The relative output power was increased up to 88% compared to that of the LED without nanosize cavities. This result couldbe attributed to an enhancement in the escape of light due to the angular randomization by the nanosize cavities and to the reducedcontact resistance due to the increased contact area between the transparent metal layers and the p-GaN.© 2005 The Electrochemical Society. DOI: 10.1149/1.2076987 All rights reserved.Manuscript submitted April 25, 2005; revised manuscript received July 19, 2005. Available electronically October 7, 2005.

Electrical and Optical Characteristics of InGaN'GaN Microdisk LEDs

Two different InGaN/GaN multiple-quantum well (MQW) microdisk light emitting diodes (μ-LEDs) with different In compositions in the MQW were fabricated. The optical output power was greatly increased with a reduction of LED size. This can be attributed to the enhanced current density and internal quantum efficiency in μ-LEDs The peak shift and the enhancement of output power were larger in μ-LED with a higher In composition in the MQW. These can be explained by a reduced piezoelectric field due to a partial strain relief and also more efficient carrier confinement due to a higher In composition in the MQWs.

Improvement in light-output power of InGaN/GaN light-emitting diodes by p-GaN surface modification using self-assembled metal clusters

To improve the escape of photons from an LED structure, we fabricated nano-sized cavities on a p-GaN surface utilizing Pt self-assembled metal clusters for an etch mask. Wet and dry etching processes were employed to produce nano-sized cavities on the p-GaN surface. The dry etching process produced cavities with diameters ranging from 200 nm to 450 nm and from 30 to 80 nm in depth, respectively. The wet etching process, however, produced small size cavities with a size of 5 ~ 6 nm. Electroluminescence measurement showed that the relative optical output powers are increased by 88% as evidenced by frontside measurement compared to those of LEDs with no nano-sized cavities. In addition, the electrical performance was also improved as evidenced by the I-V characteristic curves. This enhanced performance can be attributed to an enhancement in light escaping due to the increased light emitting area as the result of the surface cavities and also to the reduced contact resistance due to the increased contact area.