Three-segment lateral δ-doping redistribution in GaAs pHEMTs for gate-drain field relief and improved off-state...

In GaAs pseudomorphic high-electron-mobility transistors (pHEMTs) for high-power and high-linearity radio-frequency (RF) applications, significant lateral electric-field crowding at the gate-drain edge is a common issue under high drain bias, particularly during off-state and semi-off-state operation. Alleviating this peak field, however, typically leads to an increase in access resistance and degrades key RF figures of merit, resulting in an inherent robustness-performance trade-off. This work proposes a three-segment lateral δ-doping redistribution strategy in which the gate-under segment is kept unchanged, the drain-side segment is progressively reduced, and the redistributed dose is compensated by increasing the source-side segment, thereby approximately conserving the total length-weighted lateral δ-dose. Two-dimensional TCAD simulations were performed for four schemes (K1P0, K0P8, K0P6, and K0P4) using identical device geometry, material composition, and physical-model settings. DC and RF small-signal metrics were evaluated alongside an off-state robustness assessment. Electric-field mapping under a common reference bias indicates a systematic reduction in the peak lateral electric field near the gate-drain edge as the drain-side δ-doping is weakened. To enable a reproducible robustness comparison in a simulation-based study, a practical robustness metric, V_crit, is defined as the applied drain voltage at which |I_D| reaches 1 × 10^- 5 A under off-state stress (V_G= -3 V). V_crit increases monotonically from 11.99 V (K1P0) to 13.28 V (K0P8), 15.41 V (K0P6), and 19.06 V (K0P4), representing improvements of 10.8%, 28.5%, and 58.9%, respectively. This gain in robustness comes at the expense of DC/RF performance: the width-normalized on-resistance (R_on·W) increases by up to 45.4%, and the transition frequency measured at the 0.3I_DSS operating point decreases by up to 11.7%. These simulation-based results quantify the robustness-performance trade-off and provide a comparative basis for evaluating lateral δ-doping redistribution within the explored design space.