Large Schottky barriers for Ni/p-GaN contacts

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 x 10(8) cm(-2). The Schottky barrier height (q phi(B))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 q phi(B) 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. (C) 1999 American Institute of Physics. [S0003-6951(99)01014-1].