Lateral nonuniformities and the MOSFET mobility step near threshold

The reduction in extracted conductance mobility is explained in terms of an increased drain-to-source channel resistance because of lateral nonuniformities at the Si-SiO₂ interface. The effects of the nonuniformities in the inversion regime are best characterized by a quasiuniform model. C-V measurements are used to obtain independently the statistical distribution of flat-band voltages in the quasiuniform model. This information is used to simulate the two-dimensional current flow in the nonuniform inversion layer by a resistor network. The simulations are compared with accurate mobility measurements over a wide carrier-density range. The results show that the step in extracted room-temperature conductance mobility can be attributed to nonuniformities while no reduction occurs in the microscopic mobility