Depletion-mode N-polar AlN-based high electron mobility transistors with improved on/off ratios

TL;DR

This paper presents N-polar AlN-based HEMTs with significantly improved on/off ratios and high-frequency performance, achieved through an abrupt heterostructure and optimized gate leakage.

Contribution

The study introduces a novel N-polar AlN-based HEMT design with enhanced on/off ratios and reduced gate leakage compared to prior devices.

Findings

On/off ratio as high as 10,000

Saturation current over 240 mA/mm

High frequency performance limited by channel sheet resistance

Abstract

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.