Different Isolation Processes for Free-Standing GaN p-n Power Diode with Ultra-High Current Injection

Abstract

In this paper, we report on the fabrication and high performance of power p-n diodes grown on free-standing (FS) GaN substrate. The key technique to enhance the high breakdown voltage and suppress the surface leakage current is the isolation process. The mesa-structure diode is generally formed by utilizing the inductively coupled plasma reactive ion etching; however, it always induces high surface damages and thus causes a high leakage current. In this paper, we propose a planar structure by employing the oxygen ion implantation to frame the isolation region. By following the crucial process, the fabricated mesa- and planar-type diodes exhibit the turn-on voltages of 3.5 and 3.7 V, specific on-resistance (R ON A ) of 0.42 and 0.46 mΩ -cm 2 , and breakdown voltage (V B ) of 2640 and 2880 V, respectively. The corresponding Baliga's figures of merit (BFOM, i.e., V B2 /R ON A) are 16.6 and 18 GW/cm 2 , respectively. The BFOM of 18 GW/cm 2 is the highest reported value for FS-GaN diode. From the temperature dependent measurements, the planar-type diode also shows the better leakage current and thermal stability than the mesa-type diode.