Large Schottky barriers for Ni/p-GaN contacts

Abstract
Large Schottky barriers were measured for Ni contacts formed on low Mg-doped p-GaN. In order to improve leaky Schottky characteristics, low-Mg doping was examined. This provided atomically flat surfaces and a low dislocation density of 5.5×108 cm−2. The Schottky barrier height (qφB) as high as 2.4±0.2 eV and n values of 1.84±0.06 were obtained from current–voltage measurements. These results are in good agreement with the prediction that the sum of qφB of n and p types adds up to the band gap. In the capacitance–voltage measurements, a transient response of capacitance was observed. This indicates that the evaluation of deep levels close to the valence band is possible, which could result in improvement of p-GaN growth.