Impact of Multi-Bias on the Performance of 150 nm GaN HEMT for High-Frequency Applications
Résumé
This study examines the performance of a GaN HEMT with a 150 nm gate length, fabricated on silicon carbide, across various operational modes, including direct current (DC), radio frequency (RF), and small-signal parameters. The evaluation of DC, RF, and small-signal performance under diverse bias conditions remains a relatively unexplored area of study for this specific technology. The DC characteristics revealed relatively little Ids at zero gate and drain voltages, and the current grew as Vgs increased. Essential measurements include Idss at 109 mA and Idssm at 26 mA, while the peak gm was 62 mS. Because transconductance is sensitive to variations in Vgs and Vds, it shows “Vth roll-off,” where Vth decreases as Vds increases. The transfer characteristics corroborated this trend, illustrating the impact of drain-induced barrier lowering (DIBL) on threshold voltage (Vth) values, which spanned from −5.06 V to −5.71 V across varying drain-source voltages (Vds). The equivalent-circuit technique revealed substantial non-linear behaviors in capacitances such as Cgs and Cgd concerning Vgs and Vds, while also identifying extrinsic factors including parasitic capacitances and resistances. Series resistances (Rgs and Rgd) decreased as Vgs increased, thereby enhancing device conductivity. As Vgs approached neutrality, particularly at elevated Vds levels, the intrinsic transconductance (gmo) and time constants (τgm, τgs, and τgd) exhibited enhanced performance. ft and fmax, which are essential for high-frequency applications, rose with decreasing Vgs and increasing Vds. When Vgs approached −3 V, the S21 and Y21 readings demonstrated improved signal transmission, with peak S21 values of approximately 11.2 dB. The stability factor (K), which increased with Vds, highlighted the device’s operational limits. The robust correlation between simulation and experimental data validated the equivalent-circuit model, which is essential for enhancing design and creating RF circuits. Further examination of bias conditions would enhance understanding of the device’s performance.
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