GaAs0.6P0.4LED´s with efficient transparent contacts for spatially uniform light emission

Indium-tin oxide (ITO) and cadmium-tin oxide (CTO) transparent contacts have been used on GaAs0.6P0.4planar, red-light-emitting diodes. The entire emitting area of the diode can be contacted without blocking any of that area with opaque metal. Furthermore, the low sheet resistance of the transparent conducting films (2.5 to 3.5 ω/□) makes the spatial distribution of the emitted light more uniform. The spatial uniformity of the light output of LED´s fabricated with transparent contacts is compared with that of conventional LED´s. The current-voltage characteristics of the two types of LED are also compared. For an average current density of 25 A/cm², an undesirable excess voltage (> 1.2 V) is developed across the reverse-biased (n-transparent conductor)-(p-GaAs0.6P0.4) heterojunction. Procedures are described for reducing and, in some cases, completely eliminating this voltage by introducing a thin, transparent metal film between the transparent conductor and the GaAs0.6P0.4. The resulting devices have optical and electrical efficiencies comparable to those of conventional LED´s.