Assessment of Ga2O3-based Schottky diodes and hetero-junctions for applications in power electronics and UV detection

In this PhD thesis, Schottky barriers and p-n heterojunctions based on two polymorphs (β and κ phases) of gallium oxide (Ga2O3) were investigated. The study included diodes fabricated from the monoclinic β-Ga2O3 and the orthorhombic κ-Ga2O3, in both planar and vertical geometries. An extensive methodological, numerical, and experimental effort was made to get new information about the electro-optical characteristics of both polymorphs. The potential of the k-phase for solar-blind UV-C detectors, as well as that of the -phase for power devices was explored. Experimental and numerical studies on Si-doped κ-Ga2O3 provided a better understanding of the interplay between thermal treatments and trapping phenomena, a topic of considerable interest in both academic and industrial contexts. NiO/β-Ga2O3 p-n diodes developed for UV photodetection were also studied. Such type of device demonstrated satisfactory performance even for a simple circular design with a diameter of less than 300 μm, which demonstrates that NiO/β-Ga2O3 p-n diodes may be profitably used for detecting UV-C signals in daylight conditions. The extensive characterization of SnO/β-Ga2O3 p-n vertical power devices suggested a correlation between the p-type doping density of SnO and the concentration of interfacial traps in the heterojunction. The effect of such traps on the overall electrical properties of the devices was demonstrated. Finally, the electric current crowding and corresponding thermal field in planar diodes based on β-Ga2O3 and κ-Ga2O3, under forward bias, was simulated using the Sentaurus TCAD suite. The simulation evidenced the crucial role of metal/semiconductor contact resistance and showed that extra doped pockets beneath the metal contact may be effective to reduce electric current crowding and correspondingly improve the thermal field uniformity and heat dissipation.