N-polar III-nitride tunneling hot electron transfer amplifier

We report N-polar GaN-based tunneling hot electron amplifier transistors (THETA) with common-emitter modulation, ac current gain up to 1.35 operating at collector current density ~50 kA/cm², which are highest values reported to date in GaN-based hot electron transistors. Achieving higher frequency operation in the III-nitride system requires an alternative to highly-scaled GaN-based HEMTs whose transconductance and frequency are limited by electron saturation velocity. In vertical devices, channel lengths below 10nm can be achieved through heterostructure engineering. While bipolar junction transistors have been very successful in other material technologies (InP and SiGe HBTs), the poor hole doping efficiency and mobility in GaN make it difficult to achieve bipolar vertical devices. In this work, we circumvent the challenge of p-type conduction in III-nitrides by demonstrating a highly scaled vertical unipolar tunnel injection transistor. We show transistor action in an ultrascaled device with base thickness ~10 nm, which is the first experimental demonstration of tunneling hot electron transistor with N-polar orientation.