The use of indium–zinc oxide (IZO) as a transparent conduction layer (TCL) for electroplated nickel metal substrate AlGaInP light-emitting diodes with a 300×300 µm2 chip size was investigated with regard to both fabrication and effectiveness in improving light extraction efficiency. A metal system consisting of AuGe/Au was deposited to form ohmic contact dots for the n+-GaAs layer, and then an IZO film was deposited to serve as a TCL. Compared with conventional light emitting diodes (LEDs) with GaAs substrates, the proposed LEDs show an increase in light output power (i.e., ΔLop/Lop) by 116.7% at 20 mA and 168.9% at 100 mA.

The use of a refractive index matching (RIM) structure with indium zinc oxide (IZO) transparent conduction layer and SiO2 nanotube (SiO2-NT) arrays to improve light extraction of vertical structure KOH-etched GaN-based light emitting diodes (VLEDs) is demonstrated. Compared to regular VLED with KOH-roughened surface, it shows considerable gains in light emitted critical angle and light output power by 21.3° and 103% at 350 mA, respectively. These improvements could be attributed to the effectiveness of the IZO/SiO2-NT RIM scheme in ameliorating current crowding and significantly minimizing the total internal reflection effect.

The performance of vertically structured GaN-based light-emitting diodes (VLEDs) with an efficient surface roughening scheme that uses KrF laser irradiation, chemical wet etching, and an indium–zinc oxide (IZO) transparent conductive layer atop the n-GaN surface is investigated. The GaN surface, with circular protrusions and hexagonal cones, gives photons multiple opportunities to find escape cones, and the IZO film acts as a current spreading layer. The fabricated VLEDs with the proposed surface roughening scheme exhibited 79.3 and 65.1% increases in light output power at 350 and 750 mA, respectively, and showed a relatively low forward voltage compared to that of regular VLEDs.

GaN-based thin-film vertical-structured light-emitting diodes (VLEDs) with a GaO x film atop an n-GaN layer roughened via KrF laser irradiation and a TiO 2 /SiO 2 distributed Bragg reflector (DBR) are proposed and investigated. As compared with regular VLEDs with an Al reflector and without a roughened GaO x film, the proposed VLEDs with a chip size of 1 mm 2 show a typical increase in light output power by 68% at 350 mA and by 51% at 750 mA, which is attributed to the enhanced reflectivity and current blocking capability of the DBR layer, the surface roughening with circular GaN protrusions, and the formation of a surface GaO x film by KrF laser irradiation. #