An All-GaN Semiconducting-Gate HEMT for Inherent Gate-Level High-Voltage Protection and Synchronous Switching with Photoelectrically Enhanced Conductivity

We demonstrate a normally-off n-GaN/p-GaN/Al-GaN/GaN HEMT featuring a semiconducting gate (SG), i.e., an n-GaN layer overlaying the 2DEG channel as an intrinsic gate and connected to an extrinsic electrode outside the active region. With an appropriate design, the n-GaN SG will be fully depleted when the 2DEG channel is sufficiently turned on, and thereby, decouples the vulnerable intrinsic gate stack from further increase in the extrinsic gate's voltage. As a result, the SG-HEMT can tolerate extremely high-voltage external gate transients (e.g., $500-\mu\mathrm{s}$ pulses as high as 1.5 kV), enabling robust and reliable operations. Moreover, the SG structure allows using a peripheral 340-nm UV LED to create electron-hole pairs in the intrinsic gate stack. The resultant excessive holes could lead to higher 2DEG density in the channel, and thus, enhance the conductivity (reducing the on-resistance by 42.6%). With the LED driven synchronously with the gate-drive signal, the proposed SG-HEMT exhibits quick turn-off transients and im-material changes to OFF-state characteristics.