Physics-Based Analytical Channel Charge Model of InxGa1-xAs/In0.52Al0.48As Quantum-Well Field-Effect Transistors From Subthreshold to Strong Inversion Regimes

초록

This paper presents a physics-based analytical channel charge model for indium-rich InxGa1-xAs/In0.52Al0.48As quantum-well (QW) field-effect transistors (FETs) that is applicable from the subthreshold to strong inversion regimes. The model requires only seven physical/geometrical parameters, along with three transition coefficients. In the subthreshold regime, the conduction bands (E-C) of all regions are flat with finite and symmetrical QW configurations. Since the Fermi-level (E-F) is located far below E-C, the two-dimensional electron-gas density (n(2)-DEG) should be minimal and can thus be approximated from Maxwell-Boltzmann statistics. In contrast, the applied gate bias lowers the E-C of all structures in the inversion regime, yielding band-bending of an In0.52Al0.48As insulator and InxGa1-xAs QW channel. The dependency of the energy separation between E-F and E-C on the surface of the InxGa1-xAs QW channel upon VGS enables construction of the charge-voltage behaviors of InxGa1-xAs/In0.52Al0.48As QW FETs. To develop a unified, continuous and differentiable areal channel charge density (Q(ch)) model that is valid from the subthreshold to strong inversion regimes, the previously proposed inversion-layer transition function is further revised with three transition coefficients of eta, alpha and beta in this work. To verify the proposed approach, the results of the proposed model are compared with those of not only the numerically calculated Qch from a one-dimensional (1D) Poisson-Schrodinger solver, but also the measured gate capacitance of a fabricated In0.7Ga0.3As QW metal-insulator-semiconductor FET with large gate length, yielding excellent agreement between the simulated and measured results.

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