Over 3.0 GW/cm2 Figure-of-Merit GaN p-n Junction Diodes on Free-Standing GaN Substrates

This letter describes a new two-step electrode process on p-GaN and characteristics of GaN p-n junction diodes on free-standing GaN substrates with low specific ON-resistance R-on and high breakdown voltage V-B. We develop a two-step process for anode electrodes in order to avoid plasma damage to the p(+)-GaN contact layer during the sputtering process. The specific ON-resistance is further improved due to a new low-damage process. The breakdown voltage of the diodes with the field-plate (FP) structure is over 1100 V, and the leakage current was low, i.e., in the range of 10(-9) A. The specific ON-resistance of the diodes of 50 mu m in diameter with the FP structure was 0.4 m Omega . cm(2). Baliga's figure of merit (V-B(2)/R-on) of 3.0 GW/cm(2) is obtained. These are the best values ever reported among those achieved by GaN p-n junction diodes on free-standing GaN substrates.