Growth And Characterization Of TiO₂Thin Films On GaN Substrates

Titanium dioxide （TiO₂） thin films have attracted much attention for their excellentperformance, such as, optical properties, electrical properties, photocatalysis and so on.The GaN substrate, as a typical large energy gap semiconductor, shows many excellentelectric properties. With the miniaturization and high performance of electronic devicesrequirements, the thickness of the gate dielectric film is reduced to a certain degrees; itis easy to generate tunneling current, resulting in the breakdown phenomenon. Thecombination of the High dielectric parameters of TiO₂with the GaN substrate wouldimprove the devices function. It can effectively increase the reverse breakdown voltageand reduce reverse leakage current the variety of functional devices, and also improvethe problem of lattice matching between the thin films and GaN substrates.In this paper, the TiO₂films were grown on GaN substrates by the pulsed laserdeposition （PLD） technique. The targets were used commercially99.5%ceramicfabricated TiO₂. All samples were respectively grown at different substrate temperature,and under different oxygen pressure. X-ray diffraction （XRD）, Atomic force microscope（AFM）, and transmission electron microscope （TEM） were used to characterize thestructure, morphology and Interface characteristics of the TiO₂thin films.It can be seen that the rutile phase （200） TiO₂was grown on （0002） GaN substrates.And the orientation relationship between rutile TiO₂and GaN was TiO₂[001]//GaN[1120]. The XRD showed the peak becomes sharper at the substrate temperature from500°C to600°C, and the FWHM were0.78°and0.42°, respectively. With the XRD, itnoted the better crystallinity of the rutile TiO₂film was grown at higher temperature.But the RMS value was bigger, about1.286nm from the AFM. According to TEM, theepitaxial film showed a layer growth model. At the oxygen pressure of1×10-4Pa, thefilm interface was clear and smooth, presented layered structure. And the film qualitywas better than that for the oxygen pressure of10Pa, which has some detects from theatlas. In general, the quality of the film growth is strongly dependent on the substratestemperature and oxygen pressure.