Electrical properties of Ni/n-GaN Schottky diodes on freestanding m-plane GaN substrates

Abstract

The electrical properties of m-plane Ni/n-GaN Schottky diodes grown via metalorganic chemical vapor deposition were investigated. Under growth at 1,120 °C with a V/III ratio of 1,000 (growth rate of 100 nm/min), the residual Si, O, and C impurity concentrations in the m-plane GaN layer were below the secondary-ion mass spectroscopy detection limit. The surface of the Si-doped n-GaN epitaxial layer on the 5°-off m-plane GaN substrate consisted of steps and terraces. A linear correlation between the carrier concentration and the Si atomic concentration was clearly observed from 1 × 1017 to 5 × 1015 cm−3. The reverse current–voltage curves were fitted using the thermionic field-emission model at the measured carrier concentration and qϕB. The leakage current of the diodes under a reverse bias was effectively suppressed at a low carrier concentration of 4.6 × 1015 cm−3.