Epilayer thickness effect on the electrical and breakdown characteristics of vertical β-Ga₂O₃ Schottky barrier diode

The current–voltage and breakdown characteristics of Au/Ni/β-Ga₂O₃ Schottky barrier diodes were investigated as a function of β-Ga₂O₃ epilayer thickness in the range of 6–19 μm. The X-ray rocking curves indicated that the full-width half-maximum is reduced with increasing epilayer thickness, implying an improvement in the crystallinity of β-Ga₂O₃ epilayer. The barrier heights of the field-plated β-Ga₂O₃ Schottky barrier diode with epitaxial layer thickness of 6, 12, and 19 μm were obtained as 1.01, 1.03, and 1.04 eV, with the ideality factor values being 1.21, 1.19, and 1.46, respectively. The higher ideality factors could be associated with the existence of inhomogeneity at the metal–semiconductor interface. The series resistance of the Schottky diode obtained increased with increasing epilayer thickness. The Schottky diode fabricated on 19 μm thick epitaxial layer exhibited a higher breakdown voltage of 490 V. The increase in epilayer thickness led to the widening of depletion region, resulting in lower electric field over a larger distance. This could be a main cause of the enhancement of the breakdown voltage characteristics of β-Ga₂O₃ Schottky barrier diode.