Abstract: A method and apparatus for determining the carrier concentration and profile depth for pn semiconductor structures, and band discontinuities for heterojunction pn structures is disclosed. A more accurate measurement of carrier concentration and profile depth is obtained by initially measuring the pn junction intercept voltage of a pn semiconductor structure to be tested before the structure is exposed to a conventional capacitance-voltage (C-V) profiling process. The pn junction intercept voltage is employed to determine the pn junction capacitance which can then be compensated for in capacitance dependent formulae used for calculating the carrier concentration and profile depth. The intercept voltage can also be used to determine band discontinuities in a heterojunction pn structure. A fixed or retractable metal contact is employed to contact the p-type layer of a pn semiconductor structure to be tested and permit this initial measurement to be obtained.