Capacitance and Conductance for an MOS System in Inversion, with Oxide Capacitance and Minority Carrier Lifetime Extractions

Experimental observations for the In_0.53Ga_0.47As metal-oxide-semiconductor (MOS) system in inversion indicate that the measured capacitance (C) and conductance (G or G_m), are uniquely related through two functions of the alternating current angular frequency (ω). The peak value of the first function (G/ω) is equal to the peak value of the second function (-dC/dlog_e(ω) ≡ -ωdC/dω). Moreover, these peak values occur at the same angular frequency (ω_m), that is, the transition frequency. The experimental observations are confirmed by physics-based simulations, and applying the equivalent circuit model for the MOS system in inversion, the functional relationship is also demonstrated mathematically and shown to be generally true for any MOS system in inversion. The functional relationship permits the discrimination between high interface state densities and genuine surface inversion. The two function peak values are found to be equal to C_ox²/(2(C_ox + C_D)) where C_ox is the oxide capacitance per unit area and C_D is the semiconductor depletion capacitance in inversion. The equal peak values of the functions, and their observed symmetry relation about ω_m on a logarithmic ω plot, opens a new route to experimentally determining C_ox. Finally, knowing ω_m permits the extraction of the minority carrier generation lifetime in the bulk of the In_0.53Ga_0.47As layer.