A quantitative analysis of capacitance peaks in the impedance of Al/SiOx/p-Si tunnel diodes

An analytic model for the impedance properties of minority-carrier type MIS tunnel diodes is proposed. These devices can display properties different from those of the conventional MIS capacitor if the insulating layer is sufficiently thin. A simple small-signal equivalent circuit is presented that gives a clear explanation for the frequency-dependent peak occurring in the C-V characteristic. It is shown that the dynamical response of the inversion layer is the cause of this nonequilibrium behaviour. Experimental support for the proposed equivalent circuit is given by the measured capacitance of Al/SiO x /p-Si diodes with tunnel oxides grown by rapid thermal oxidation (RTO). The capacitance peak is studied as a function of frequency and oxide layer thickness between 2 and 3 nm. A good agreement between the experimental and simulated results is found for diodes which received a post-oxidation anneal in H 2 .