Use of Anisotropic Laser Etching and Transparent Conducting Layer to Alleviate Current Crowding Effect in Vertical-Structured GaN-Based Light-Emitting Diodes

An anisotropic laser etching to the surface layer (n-GaN) of vertical-structured GaN-based light-emitting diodes (LEDs) associated with a transparent conducting layer (TCL) to release current crowding effect (CCE) for better light emission uniformity and higher optical efficiency is proposed and demonstrated. The theory behind the proposed scheme was verified by a two-dimensional device simulator (ISE-TCAD), which indicates that immune of CCE would be possible once an optimal combination of the concave-structured n-GaN layer and TCL has been achieved. In experiments, 40-mil LEDs with an anisotropic etching area of 800 μm in diameter, an etching depth of 1.75 μm at center, and a 300-nm-thick Indium-Zinc-Oxide (IZO) layer have been successfully prepared. Typical improvement in light output power by 26% at an injection current of 350 mA as compared to the one without anisotropic etching has been obtained.