Rapid-thermal-annealing-induced microstructural evolution of Au/Ni/β-Ga2O3 Schottky diodes correlated with their electrical properties

Abstract

This study investigated the rapid thermal annealing (RTA)-induced phase and microstructural evolution of Au/Ni/ β -Ga 2 O 3 Schottky diodes to demonstrate their effect on the diodes’ electrical properties in the temperature range of 400–700 °C. Annealing at 500 °C led to a reaction between the Au and Ni films, forming Au-rich Au 3 Ni and Ni-rich AuNi 3 phases along with a homogeneous AuNi alloy phase with a smooth surface and interface morphology. Only the Au 2 Ni phase formed after RTA at temperatures above 600 °C. Reactions did not occur between the Ni/Au metal contacts and the Ga 2 O 3 substrate, regardless of the RTA temperature. The Au/Ni/ β -Ga 2 O 3 Schottky diode annealed at 500 °C exhibited improved rectifying behavior with a large barrier height (1.22 eV) and large breakdown voltage ( V br ) of 460 V, which may be associated with the formation of Au-Ni alloy films with a smooth surface morphology and abrupt interface with the Ga 2 O 3 substrate. The Schottky diode behavior began to degrade upon RTA at 600 °C, which is attributed to the initiation of degradation of the surface and interface morphology of the Au 2 Ni alloy film. The deterioration of the Schottky behavior with the drastic increase of the reverse leakage current and sharp drop of V br upon RTA at 700 °C is attributed to the severe deterioration of the interface and surface morphologies, such as the roughened surfaces caused by agglomeration and void formation with the grain boundaries serving as high leakage current paths. • RTA-induced device performance of Au/Ni/ β -Ga 2 O 3 Schottky diode was investigated. • No reactions occurred between Ni/Au films and β -Ga 2 O 3 for all RTA temperatures. • RTA at 500 °C induced a significant reaction between the Au and Ni films. • High breakdown voltage of 460 V was obtained on annealing at 500 °C. • Above 600 °C, device performance deteriorated due to structural degradation.