This letter utilizes ultrasonic spray pyrolysis (USP) to deposit Al 2O3 as the passivation layer of GaN light-emitting diodes (LEDs). The composition of Al2O3 is analyzed by X-ray photoelectron spectroscopy. The refractive index and transmittance of USP-grown Al2O3 are investigated. The thickness of Al 2O3 is determined to be 70 nm, which is close to the optimum from antireflection theorem calculation for the wavelength of 455 nm. The coverage quality and thickness are confirmed by transmission electron microscopy. The light output power (LOP) of USP-grown-Al2O 3-passivated InGaN/GaN LED is improved from 321 mW to 347 mW compared with an LED without passivation. The forward voltage (VF) and series resistance (Rs) are not subject to significant variations but the shunt resistance (RSH) is increased after Al2O3 passivation. LED chips with Al2O3 and SiO2 passivation are packaged as LED lamps. Devices passivated by USP-grown Al 2O3 show slightly better LOP performance than those passivated by plasma-enhanced chemical vapor deposition-grown SiO2.
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