【Device Papers】Mitigation of short-channel effects in ultra-scaled AlN/β-Ga₂O₃ high electron mobility transistors

      Researchers from Birla Institute of Technology and Science-Pilani have published a dissertation titled " Mitigation of short-channel effects in ultra-scaled AlN/β-Ga₂O₃ high electron mobility transistors " in IEEE Transactions on Device and Materials Reliability.

Abstract

      In recent times, there has been an immense amount of interest in the utilization of gallium oxide (Ga₂O₃) in power electronics because of the excellent figure of merit (FOM) values it exhibits, mostly as a consequence of its wide bandgap of almost 5 eV. Many different Ga₂O₃-based field-effect transistors (FETs) have been realized, and a number of devices have also been proposed in the literature. Among these devices, high electron mobility transistors (HEMTs) are particularly advantageous in realizing the high-power RF capabilities of Ga₂O₃, as they typically exhibit higher values of sheet carrier density (n_s) and effective mobility (μ_eff). Of the proposed structures, the AlN/β-Ga₂O₃ polar HEMT is one of the most promising, with simulations indicating n_s of the order 10¹³ cm⁻² and excellent RF parameter values. In this work, we have performed a proof-of-concept simulation of an AlN/β−Ga₂O₃ polar HEMT, having gate length (L_G) of 50 nm to maximize RF performance, with the aim of benchmarking this device’s performance and exploring its design space. We note poor subthreshold characteristics and aim to improve subthreshold slope (SS), ON-OFF current ratio (I_ON/I_OFF) and drain-induced barrier lowering (DIBL) coefficient without significantly compromising the RF performance. To this end, we implement an (Al_xGa_1−x)₂O₃ back barrier layer to improve carrier confinement and mitigate OFF-state leakage current. SS and DIBL values of 122 mV/dec and 87 mV/V were obtained for an optimized structure having the back barrier, with an ON-OFF ratio (I_ON/I_OFF) of the order 10⁶−10⁷. While the implementation of the back barrier initially produced improvement in the values of cutoff frequency (fₜ) and maximum oscillation frequency (f_max), the optimized structure having the best subthreshold performance exhibited lower fₜ and f_max values of 66.3 GHz and 74.8 GHz respectively, though these are still superior to the highest reported values for experimentally realized Ga₂O₃-based planar FETs. These results vindicate the interest in developing AlN/β−Ga₂O₃ polar HEMTs as reliable high-performance RF devices, while the improved subthreshold characteristics also increase the applicability of these devices for use in biosensors.

DOI：

https://doi.org/10.1109/TDMR.2026.3723461