Investigation of opto-dielectric properties of Ti-doped Ga2O3 thin films

• Doping of Ti to Ga2O3 can be described by Ti→Ga-OxideTiGa·+VGa
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• It is possible to engineer Eg of Ga2O3:Ti solid solution films by Ti content.
• Utmost AC-conduction optosensitivity was in 6–10% doping attaining large values 700–800%.
• 2–6% Ti-doped Ga2O3 are dielectrics of ∼109 Ω cm with low permittivity 1.6–1.7.

Several Ti-incorporated Ga-oxide (Ga2O3) thin films with different amounts of Ti contents have been prepared by vacuum evaporation method on glass and silicon substrates. The Ti incorporation level was measured with energy dispersion X-ray spectroscopy (EDX) method. The crystalline structure of the prepared films was determined with X-ray diffraction method. Experimental data indicate that Ti4+ ions doped in host Ga2O3 form solid solutions (SS) even with so large Ti% content ∼10.4% wt. All the prepared solid solutions have the known orthorhombic (ɛ-phase) phase of Ga2O3. The doping controls the optical and electrical properties of the host Ga2O3. It was found that the bandgap of the prepared undoped Ga oxide is 5.23 eV, which was decreased monotonically with increasing of Ti doping level so that it is possible to engineer the bandgap. Furthermore, the electrical measurements show that with Ti doping, it is possible to turn the high-k Ga oxide into low-k dielectric material. The optical sensitivity of the capacitance, dissipation factor, and ac-conductance of the Ga2O3:Ti films grown on Si was studied as a function of Ti-doping level. It was observed that the prepared Ga2O3:Ti film with 6–10% doping level has the highest photosensitivity among the other samples.

The dependence of the optosensitivity of capacitance, dissipation factor, and ac-conductivity for the constructed (Au/Ti-doped Ga2O3/n-Si) MOS capacitor measured at accumulation gate voltage +2 V with signal 50 mV/1 MHz and the light intensity of 266 W/m2.Figure optionsDownload as PowerPoint slide