Photoelectrochemical sidewall etching enhances light output power in GaN‐based light emitting diodes

Abstract

PACS 81.15. Gh, 81.65.Cf, 82.45.Vp, 82.50.Hp, 85.60.Jb InGaN/GaN multi-quantum-well light-emitting diodes (MQW LEDs) are grown through a metal-organic chemical vapor deposition (MOCVD) System. The fabricated GaN-based LED wafers are treated with a photoelectrochemical (PEC) wet etching process using a Hg lamp illumination and KOH solution. The band-gap selected wet etching process of InGaN/GaN MQW layer was observed from the mesa sidewall between the p-type and n-type GaN interface which has the 4.2 µm/hr lateral etching rate. The emission wavelength of the etching treated LED and standard LED were located at 458 nm. The light output power of the PEC etching LED had 2.04, 5.94, and 1.73 times enhancement measured from the from-side, lateral-direction, and back-side compared with the standard ones. The light output power have stronger enhancement caused by forming the triangle-shaped air holes located at the active layer region, grain-like roughening surface and nano-scale triangle pits on the mesa sidewall. The light scattering by this roughening sidewall was increased to enhance the light extraction efficiency. This PEC sidewall etching process is suitable for high power Nitride-based LEDs lighting applications.

Free-Standing GaN Layer by Combination of Electrochemical and Photo-Electrochemical Etching

“…21,22) In the back-side illumination, the oxidation takes place at the interface between the surface and undoped GaN layer because the UV light passes through the substrate and then is absorbed in the undoped GaN layer. 23,24) Figure 2(b) shows cross-sectional SEM image of the sample for which only the back-side PEC etching without EC etching was performed. The etching front laterally penetrated from the sample edge (right side) inside the uid GaN undercutting it.…”

Optical Output Power Enhancement of Gallium Nitride Light-Emitting Diodes with Microlens Array on p-GaN Layer and Wave-Patterned Sidewalls by Gas-Assisted Focused Ion Beam Etching

“…[2][3][4][5][6] Some groups have proposed various dry etching methods for performing patterning on the top surface and sidewalls, but the facets produced are rough and nonuniform awing to the overetching of an oxide mask during pattern transfer. 7,8) For wet etching, Pt metal clusters used as a mask may lead to the successful microroughening of GaN-LEDs without damaging the p-GaN surface; 9) such clusters are not capable of fabricating sophisticated patterns, such as a microlens array.…”