Effect of surface treatment on the performance of vertical-structure GaN-based high-power light-emitting diodes with electroplated metallic substrates

Large-area (0.6 × 0.6 and 1 × 1 mm²) highly-efficient GaN-based light-emitting diodes (LEDs) with a vertical-conducting structure (VM-LEDs), using a patterned laser lift-off technique and a Ni electroplating process as well as a surface treatment of the top n-GaN epilayer by plasma and chemical etching, were successfully fabricated and investigated. Compared to regular LEDs of the same size, both the forward voltage drop and the light output power (L_op) of the VM-LED were substantially improved. With inductively coupled plasma (ICP) etching followed by an additional KOH etching and an HF/HCl treatment on the n-GaN layer, an increase in L_op by 227% (195%) at 350 (800) mA has been achieved for the (1 × 1 mm²)-sized VM-LEDs.