Amorphous titanium oxide (a-TiOx:OH) films prepared by plasma-enhanced chemical-vapor deposition at 200 and 25 °C are in turn deposited onto the GaN-based light-emitting diode (LED) to enhance the associated light extraction efficiency. The refractive index, porosity, and photocatalytic effect of the deposited films are correlated strongly with the deposition temperatures. The efficiency is enhanced by a factor of ∼1.31 over that of the uncoated LEDs and exhibited an excellent photocatalytic property after an external UV light irradiation. The increase in the light extraction is related to the reduction in the Fresnel transmission loss and the enhancement of the light scattering into the escape cone by using the graded-refractive-index a-TiOx:OH film with porous structures.

The relationship between the electrical, optical and material properties of transparent and conductive oxide films prepared by rf cosputtering indium–tin oxide (ITO) and zinc oxide (ZnO) targets has been investigated. The evolution from polycrystalline structure of an undoped ITO film to an amorphous-like ZnkIn2O3+k structure obtained from ZnO-doped ITO films is found to be responsible for the marked improvement in the electrical properties. A low surface roughness is also achieved from this amorphous structure. However, both electrical property and surface uniformity begin to degrade with increasing rf cosputtering power on the ZnO target that corresponds to a high atomic ratio of Zn/(Zn + In). The degradation mechanism is attributed to the appearance of a microcrystalline ZnO structure that is detrimental to the film resistivity. Furthermore, optical band gap calculated from the absorption edge of such cosputtered films also decreases with increasing ZnO impurities.

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GZO transparent conductive thin films were deposited by the direct current magnetron sputtering method from a ZnO target doped with Ga2O3 of 3wt% on glass slide substrates under high pressure of argon. The effect of substrate temperature on the GZO film’s morphology, optical and electrical properties is investigated by using scanning electron microscopy (SEM), UV spectrophotometer, four point probe and Spectroscopic Ellipsometer. The results showed that GZO thin films with high quality could be fabricated under the high pressure of argon.When substrate temperature is 250°C or below, surface morphology of thin films can be significantly improved.With the increase of substrate temperature, the crystal grain become larger, the crystal boundaries narrow and become clear, and reach a best case at 250°C. At the same time, the resistivity of GZO thin films decrease and reach the minimum which is 1.099×10-3 Ω•cm at 300°C while the average transmittance increase to 90%. Consequently, the properties of morphology began to get worse with the increase of temperature above 300°C.