Electrical characteristics of contacts to thin film N-polar n-type GaN

The electrical characteristics of metallization contacts to a thin film N-polar n-type GaN layer fabricated by a laser lift-off process combined with a dry etching are investigated. It is shown that for Pt Schottky contacts, the Schottky barrier height of the N-polar GaN is 1.27 eV, which is larger than that (1.23 eV) of reference Ga-polar GaN. Ti/Al Ohmic contacts to the N-polar GaN experience thermal degradation even at 400 degrees C. Such annealing-induced degradation is explained in terms of the presence of the complex surface states of the N-polar GaN, which consists of impurities and process-induced donorlike and acceptorlike defects.