AlGaInP thin-film LED with ITO omni-directional reflector

Four kinds of thin-film light emitting diodes (LEDs), with different metal reflectors and different thickness indium tin oxide (ITO) layers, were fabricated from the same AlGaInP/GaAs epitaxial layer. For comparison, three kinds of LEDs have the same ITO/AuZnAu reflector, but have different thickness of ITO film 65, 90 and 270nm, respectively. The device with 65nm ITO film provides the best luminous intensity-current (L-I) and injection current-forward voltage (I-V) performance, which has the luminous intensity of 149.2 mcd (@20mA) and the forward voltage of 2.15v (@20mA). In addition, two kinds of LEDs have the same 90nm ITO layer, but have different reflector ITO/AuZnAu and ITO/Au, respectively. The LED with ITO/AuZnAu reflector has better optical and electrical properties. The possible reason may be the diffusion of Zn content into the ITO layer and GaP layer. The influences of Zn content and the thickness of ITO film to the optical and electrical properties of the LEDs are discussed in this paper.