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<p>This study presents a unified experimental and equivalent-circuit analysis of the thermal and multi-bias behavior of an InGaAs-channel GaAs pHEMT. Unlike studies limited to selected DC or RF characteristics, the present work correlates measured DC behavior, S-parameters, extracted extrinsic and intrinsic small-signal parameters, delay constants, high-frequency figures of merit, Zero Temperature Coefficient (ZTC) behavior, and RF stability over −&#xa0;25 to 150&#xa0;°C. The drain current I<sub>ds</sub> decreases from 278 to 234&#xa0;mA/mm with increasing temperature, g<sub>m</sub> decreases from 298 to 242 mS/mm and V<sub>T</sub> shifts from about −&#xa0;0.74 to −&#xa0;0.85&#xa0;V. A ZTC point, i.e. a thermally stable current-bias region at V<sub>gs</sub> = −&#xa0;0.55&#xa0;V, is identified. The equivalent circuit extraction shows that R<sub>gs</sub>, R<sub>gd</sub> and R<sub>ds</sub> increase with temperature due to the decrease in conductivity, increase in carrier scattering and changes in contact related resistance, while C<sub>gd</sub> and C<sub>ds</sub> decrease and C<sub>gs</sub> increases for the studied bias range. The intrinsic transconductance g<sub>mo</sub> decreases from 59.88 to 40.36 mS, the time constants τ<sub>gm</sub> and τ<sub>gs</sub> increase while τ<sub>gd</sub> decreases due to the reduction in C<sub>gd</sub> partially compensates the increase in R<sub>gd</sub>. The RF performance degrades with temperature: S<sub>21</sub> decreases from 15.8 to 13.3&#xa0;dB, Y<sub>21</sub> decreases from 67.08 to 50.6 mS, f<sub>t</sub> decreases from 29.2 to 15.1&#xa0;GHz, f<sub>max</sub> decreases from 89.4 to 46.9&#xa0;GHz. The stability factor K increases from 1.16 to 1.37, which corresponds to an improved unconditional-stability margin at higher temperature. These results provide practical guidance for thermally aware bias selection in GaAs/InGaAs pHEMT-based RF circuits.</p>

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Thermal and bias dependencies of InGaAs pHEMT performance: insights from DC, RF, and equivalent circuit analysis

  • 期刊论文

  • 发表日期：

    2026年7月22日

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  • Mohammad Abdul Alim

摘要

This study presents a unified experimental and equivalent-circuit analysis of the thermal and multi-bias behavior of an InGaAs-channel GaAs pHEMT. Unlike studies limited to selected DC or RF characteristics, the present work correlates measured DC behavior, S-parameters, extracted extrinsic and intrinsic small-signal parameters, delay constants, high-frequency figures of merit, Zero Temperature Coefficient (ZTC) behavior, and RF stability over − 25 to 150 °C. The drain current Ids decreases from 278 to 234 mA/mm with increasing temperature, gm decreases from 298 to 242 mS/mm and VT shifts from about − 0.74 to − 0.85 V. A ZTC point, i.e. a thermally stable current-bias region at Vgs = − 0.55 V, is identified. The equivalent circuit extraction shows that Rgs, Rgd and Rds increase with temperature due to the decrease in conductivity, increase in carrier scattering and changes in contact related resistance, while Cgd and Cds decrease and Cgs increases for the studied bias range. The intrinsic transconductance gmo decreases from 59.88 to 40.36 mS, the time constants τgm and τgs increase while τgd decreases due to the reduction in Cgd partially compensates the increase in Rgd. The RF performance degrades with temperature: S21 decreases from 15.8 to 13.3 dB, Y21 decreases from 67.08 to 50.6 mS, ft decreases from 29.2 to 15.1 GHz, fmax decreases from 89.4 to 46.9 GHz. The stability factor K increases from 1.16 to 1.37, which corresponds to an improved unconditional-stability margin at higher temperature. These results provide practical guidance for thermally aware bias selection in GaAs/InGaAs pHEMT-based RF circuits.