Ga-Doped ZnO Grown by Atomic Layer Deposition and the Application to Blue Light-Emitting Diodes as a Current Spreading Layer

The Ga-doped ZnO (GZO) thin films were grown by atomic layer deposition (ALD) on glass substrates at different substrate temperatures. The GZO films deposited at the optimized substrate temperature of 325°C have the resistivity of ∼4 × 10 −4 Ω-cm and the transmittance of over 90% in the visible spectra. The GZO films applied to GaN blue light-emitting diodes (LEDs) as the current spreading layer exhibit a forward voltage of 3.1 V, a series resistance of 7.8 Ω/□, and a light output power of 10.7 mW at 20-mA injection current, which are comparable to the blue LEDs with ITO film.