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

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 mesaand 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 (VB) of 2640 and 2880 V, respectively. The corresponding Baliga's figures of merit (BFOM, i.e., V2B/RONA) 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.