Structural, optical, and opto-dielectric properties of W-doped Ga2O3 thin films

A layer-by-layer deposition technique of Ga2O3 and WO3 by vacuum evaporation method on glass and silicon substrates and subsequent annealing in oxygen atmosphere to form W-doped Ga2O3 (or Ga2O3:W) films was attempted here. The W doping level was measured by the energy dispersive X-ray fluorescence radiographic analysis. The crystalline structure of Ga2O3:W films was determined by the X-ray diffraction method. Experimental data indicate that W6+ ions doped in host Ga2O3 forming solid solutions (SS), in which the molar ratio (r) of W to Ga is 9.6, 13.4, 18.2, 22.7 and 30.4%. All the prepared SS have the known beta-Ga2O3 crystalline structure. This doping controls the optical and electrical properties of the host Ga2O3. The optical properties of the prepared Ga2O3:W films were studied by UV-VIS-NIR absorption spectroscopy method from which the bandgap was determined. In general, it was found that the prepared Ga2O3:W films are wide-bandgap semiconductors with bandgap 4.69-4.47 eV and have dielectric properties. The optical sensitivity of the capacitance, dissipation factor and ac-conductance of the Ga2O3:W films grown on Si was studied as a function of W-doping level. It was observed that the prepared Ga2O3:W film of r = 22.7% has the highest photosensitivity amongst the other samples.