Ultra-low leakage and high breakdown Schottky diodes fabricated on free-standing GaN substrate

Vertical Schottky diodes were fabricated on the bulk GaN substrate with decreasing impurity concentration from N-face to Ga-face. An array of circular Pt Schottky contacts and a full backside Ti/Al/Ni/Au ohmic contact were prepared on the Ga-face and the N-face of the n-GaN substrate, respectively. The Schottky diode exhibits a minimum specific on-state resistance of 1.3 mΩ cm2 and a maximum breakdown voltage of 600 V, resulting in a figure-of- merit of 275 MW cm−2. An ultra-low reverse leakage current density of 3.7 × 10−4 A cm−2 at reverse bias of 400 V was observed. Temperature-dependent I–V measurements were also carried out to study the forward and reverse transportation mechanisms.