Impact on on-resistance of p-n junction diodes by using heavily Ge-doped GaN substrate

Abstract

The characteristics of p-n junction diodes on heavily Ge-doped substrates were compared with those on conventional Si-doped substrates. A large decrease in on-resistance was observed which greatly exceeded the component due to the lower resistance of the Ge-doped substrate. This result implied an occurrence of a strong conductivity modulation by the heavily doped substrate. Current-density dependence on the anode-electrode diameter could be minimized by the use of the substrate. No significant difference was observed in the breakdown voltage even when the doping concentration in the substrate was increased. It has been clarified that the heavily Ge-doped GaN substrate is essential for low on-resistance and large size GaN power devices.