Abstract
We report on the fabrication and evaluation of leakage current based on GaN p-n junctions grown by metalorganic vapor phase epitaxy over sapphire. Si and Mg were used as n- and p-type dopants, respectively. Reactive ion etching was used to define mesas of different sizes and metal ohmic contacts were fabricated. Reverse dark current of 15 pA/mm2 was measured under -8 V bias at room temperature, and that of 900 pA/mm2 was measured under -5 V bias at 480 K. Surface leakage along the mesa sidewalls is suggested to be the main source of leakage under a low bias voltage, and tunneling effects appear to be the main reason for junction breakdown.