Capacitance Compact Model for Ultrathin Low-Electron-Effective-Mass Materials

We present a compact model to calculate the capacitance of undoped high-mobility low-density-of-states materials in double-gate device architecture. Analytical equations for estimating the subband energies, while taking the effect of wavefunction penetration into the gate oxide and the effective mass discontinuity, are presented for the first time in a compact modeling framework. The surface potential equation for a two subband system is solved, assuming Fermi-Dirac statistics, and compared to numerical Schrodinger-Poisson simulations. The importance of accurately treating the charge profile distribution is illustrated, and an analytical expression for the effective oxide thickness to model the charge centroid is developed.