We report N-polar AlN-based high-electron mobility transistors (HEMTs) with a GaN channel thickness of 5.2 nm on N-polar AlN on sapphire. The threshold voltage is around -2.4 to -3.0 V with saturation currents over 240 mA/mm and on/off ratios as high as 10,000, much higher than previously reported N-polar AlN-based HEMTs. The high on/off ratio is attributed to the use of an abrupt AlN/GaN heterostructure with a dedicated AlN transition layer, together with improved gate leakage. The high frequency properties as well as the on-resistance of ~20 Ohm mm are all limited by the 2000 Ohm/square sheet resistance of the channel layer.
@article{arxiv.2605.14329,
title = {Depletion-mode N-polar AlN-based high electron mobility transistors with improved on/off ratios},
author = {Xu Yang and Sheng Zhang and Ke Wei and Xinhua Wang and Xinyu Liu and Itsuki Furuhashi and Markus Pristovsek},
journal= {arXiv preprint arXiv:2605.14329},
year = {2026}
}