| dc.description.abstract | Metal-oxide-semiconductor capacitors (MOSCAP) based on the β phase of gallium oxide (β-Ga2O3) were pursued for future power electronic devices. Two surface orientations of β-Ga2O3 were investigated, i.e. (010) and (-201), while for the oxide layer aluminium oxide (Al2O3) was deposited using atomic layer deposition (ALD). From the current-voltage (IV) and capacitance-voltage (CV) measurements, it was found that the sample with the (010) surface orientation showed better rectification and lower density of interface states. On the basis of this result, MOSCAPs based on (010) β-Ga2O3 were fabricated and post deposition annealing employed, and the results were compared with a more mature material for power electronics, namely 4H-silicon carbide (4H-SiC). From the current-voltage (IV) and capacitance-voltage (CV) measurements, the β-Ga2O3 MOSCAP samples exhibit smaller flat band voltage than 4H-SiC MOSCAPs and did not show any kink in depletion. It was also demonstrated that the increase of the annealing temperature improves the interface states between 4H-SiC and Al2O3, but conversely, it degraded the MOSCAP properties in β-Ga2O3. Information on bulk and interface defect states of β-Ga2O3 and 4H-SiC MOSCAP was obtained from the peak of the Deep Level Transient Spectroscopy (DLTS) spectra, and thermal dielectric relaxation current (TDRC) was also attempted. Signatures were obtained from the DLTS spectra originating from defects present in the bulk and closer to the interface. Furthermore, H+ irradiation was used to examine general defect states and intrinsic defects states of β-Ga2O3. A peak appeared in the recovery process in response to irradiation. This irradiation induced peak indicate an intrinsic origin, and labeled E2* in a recent study(1). Finally, MOS field effect transistors (MOSFETs) and metal semiconductor FETs (MESFETs) have been attempted for wider understanding the β-Ga2O3 for power devices. | eng |