Download 10-1 V-Shaped Channel for Record GaN Threshold Voltage

V-Shaped Channel for Record GaN Threshold Voltage: Power transistors made from gallium nitride
(GaN) alloys instead of silicon are promising alternatives for high-power applications. Planar
AlGaN/GaN transistors on silicon substrates are commercially available with blocking voltages of ≤600
V, but Panasonic researchers will describe vertical GaN devices on a bulk GaN substrate (pGaN/AlGaN/GaN ) that demonstrated a record-setting 1.7 kV threshold voltage plus a remarkably low
on-state resistance of 1.0 mΩcm2. One day such efficient devices may eliminate the need for liquid
cooling in high-power electronic systems, thereby reducing their size, weight, complexity and cost. To
achieve this performance, the researchers created a “semipolar” gate structure that propels charge carriers
with great efficiency. They plasma-etched V-shaped grooves into an n-GaN drift layer atop the substrate.
Because these grooves were cut at a slant, they exposed a second facet of the crystalline GaN material and
thereby created the possibility of semipolar operation. The researchers then expitaxially grew pGaN/AlGaN/GaN layers in these grooves and built a “slanted” channel with the gate on top.
Schematic cross-sections of the lateral p-type gate transistor without and with the slanted channel are
shown at left, along with their measured transfer characteristics. The lateral transistor with a slanted
channel exhibits 1.5 V larger VTH than the one without slanted channel.
(Paper #10.1, “1.7 kV/1.0 mΩcm2 Normally-Off Vertical GaN Transistor on GaN Substrate with Regrown pGaN/AlGaN/GaN Semipolar Gate Structure,” D. Shibata et al, Panasonic)