Reverse-Conducting Normally-OFF Double-Channel AlGaN/GaN Power Transistor With Interdigital Built-In Schottky Barrier Diode

Low-loss reverse-conducting normally-OFF double-channel AlGaN/GaN power transistor with the built-in Schottky barrier diode (SBD) has been systematically studied. This device features the MOS-gate section and SBD-anode section paralleled to an interdigital layout along the gate width direction. A common access region that conducts current at both forward and reverse ON-states is employed, which is beneficial to reduce the conduction loss. With a MOS-HEMT/SBD finger width of 4 mu m/2 mu m and a total width ratio of 2:1, the device exhibits a threshold voltage of +0.8 V at a drain current of 10 mu A/mm and a low forward ON-resistance of 12.1 Omega . mm. The Schottky metal contacts 2-DEG directly, which results in a low reverse turn-on voltage of -0.6 V (at -1 mA/mm) and low reverse ON-state voltage of -1.7 V (at -50 mA/mm). A leakage suppression MOS field plate (FP) is applied to shield the Schottky contact from the strong electric field, leading to a low OFF-state leakage current of 14 nA/mm at +100-V drain bias and a high breakdown voltage (BV) of +698 V. The finger width and the number of fingers should be optimized. A narrow finger width benefits the current sharing at the access region, while the increasing number of fingers introduces more Schottky depletion regions along the gate width direction that degrade R-ON.