CAPACITANCE VOLTAGE MEASUREMENTS ON SCHOTTKY DIODES WITH POOR OHMIC CONTACTS

The evaluation of Schottky-diode capacitances or reliable free-carrier concentration profiles in doped semiconductors by admittance measurements need a time- and money-consuming diode structuring process since the rectifying and ohmic contacts are produced separately. The formation of both contacts simultaneously during the same process step reduces costs. However, since alloying cannot be done, the diodes exhibit a poor ohmic contact. Consequently, minority carrier influence, series resistance effects, and deep level influence lead to frequency-dependent admittances. In this work, frequency-dependent admittance analysis on such diodes and a simple small-signal equivalent circuit model are used to evaluate space-charge capacitances reflecting only the free carriers of the doped material. This method is useful for the automatic routine control of semiconductors. The minority carrier, deep level, and series resistance influence on the diode admittance is reviewed.