III-nitride-based hot electron transistors (HETs) offer a significant promise as high-speed, high-power devices, but their performance has been limited to below that of competing technologies. Here, we report on a HET with current density > 440 kA/cm2 and common-emitter current gain >20. Polarization engineering of the emitter stack was used to allow for high-current collimated electron injection from the emitter with relatively low turn-on voltage. The use of only polarization charge in the undoped 10 nm-thick base allowed for high gain through minimization of scattering with atomic layer etching contact fabrication used to lower base access resistance.