Over 3.0 $\hbox{GW/cm}^{2}$ 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
_οn
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 μm in diameter with the FP structure was 0.4 mΩ · 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.