Electron-beam and sputter-deposited indium-tin oxide omnidirectional reflectors for high-power wafer-bonded AlGaInP light-emitting diodes

Performance variation of 1 mm2 high-power wafer-bonded AlGaInP light-emitting diode (LED) with an emission wavelength of 630 nm induced by E-beam and sputter-deposited indium-tin oxide (ITO) films, one component of triple-layer omnidirectional reflectors (ODRs), has been investigated in detail. The entire ODRs consist of p-GaP, dispersive dot contacts of AuAuBeAu acting as ohmic contacts, an intermediate low-refractive index ITO, and a silver (Ag) layer. The results show that annealing under nitrogen atmosphere yields a much rougher surface for the E-beam evaporated ITO than that for the magnetron sputtered one, which leads to a lower reflectivity of the ITO/Ag system. A similar resistivity of the two ITO films after annealing confirms no influence on the current-voltage characteristics of the corresponding devices. The smoother surface morphology of the sputter-deposited ITO after annealing enhances the light output power of 18% as compared to the one with the E-beam evaporated ITO at 350 mA for the ITO ODR-based AlGaInP LEDs.