Structure optimization and fabrication of GaN quasi-vertical diode

Abstract

In order to improve the performance of GaN-on-Si quasi-vertical diodes, this letter demonstrates GaN quasi-vertical diodes with different anode area, the anode-cathode spacing (Lac) and layout design of electrodes (circular and finger type). By optimizing the fabrication process, the specific contact resistivity of ohmic contact between metal electrodes and n-GaN (ND~1×1019cm−3) is 3.38×10−5Ω.cm2. Comparing devices with different structures shows that the forward current density of the diodes increases with the decrease of the anode area. The increase of anode-cathode spacing leads to the increase of on-resistance. The forward J-V characteristics of the PN diodes with circular and finger-type anode are compared, the forward current density of the finger-type diode is larger than that of the circular type diode. By optimizing the device structure, a circular GaN quasi-vertical diode with the turn-on voltage of 3.2V (@1A/cm2), the specific on-resistance of 0.97mΩ.cm−2 and the on/off current ratio of 109 was obtained.