On the condition of strong inversion and terminal voltages in MOS structures with nonuniform and degenerate doping

An expression is derived which relates the potentials at the surface and the depletion layer edge at the onset of strong inversion to the applied voltage between source and bulk of an MOS structure. The expression is valid for degenerate and nonuniformly doped substrates. A new definition of strong inversion is proposed which reduces to the definition given by Doucet and van de Wiele under nondegenerate conditions. A simplified structure is considered which allows the MOS device to be analyzed using a one-dimensional model. The role of metal-semiconductor contacts and the assumptions involved in the analysis are discussed.