Abstract: The influence of frequency characteristics of devices is complex. The effects of AlN barrier thickness, gate length, gate-drain spacing and work function on the frequency characteristics of AlN/β-Ga₂O₃ high electron mobility transistor (HEMT) were studied by Sentaurus TCAD in this paper. The following conclusions are obtained: as the thickness of the AlN barrier layer increases from 10 nm to 25 nm, the cutoff frequency (f_T) and maximum oscillation frequency (f_max) rise by 18 and 17 GHz respectively. The decrease of gate capacitance is the main reason for the increase of f_T. Furthermore, it was found that the thinner barrier layer enhanced the gate’s ability to control the channel electrons. When the gate length is scaled down from 0.9 μm to 0.1 μm, f_T and f_max increase by 84 and 98 GHz, respectively, representing a far more profound influence on frequency characteristics than the barrier layer thickness. However, when the gate length fell below 0.1 μm, short-channel effects emerged. As the gate-drain spacing increase, f_T exhibits a slight decrease. Coupled with the concurrent reduction in source resistance, this led to a synchronized trend in f_max and f_T only when the gate-source voltage (V_GS) exceeds -1.2 V. The work function, on the other hand, has minimal impacts on f_T and f_max, but an increase in the work function positively influenced the device’s pinch-off characteristics. In summary, this paper indicates that by shortening the gate length while concurrently augmenting the thickness of the AlN barrier layer, gate-drain spacing, and work function, one can enhance the frequency characteristics while also improving the pinch-off characteristics of the device, which has certain guiding significance for the design of HEMT devices.

Key words: β-Ga₂O₃, AlN, HEMT, cutoff frequency, maximum oscillation frequency