A contactless p-n junction leakage measurement method is described, which uses specialized very-high-frequency oscillator circuitry. This circuitry utilizes the eddy current loading effect, via inductive coupling, in order to determine the leakage-dependent decay time of the photoinduced voltage across the diffused p-n junctions in a silicon wafer.

The contactless measurement is made under low forward bias conditions (≤ 10 mV), in such a way that this measurement and the contacting reverse leakage, measured at 100 mV, will both be functions of generation-recombination processes in the junction depletion region. Detectable signals were made possible by low-noise circuitry and by the increase in junction eddy currents from induced voltages across the diffused regions.

The following model was derived from basic circuit theory, which relates the contactless decay time measurement, τ, to the conventional contacting reverse leakage, J₀ J0=CkT∕qτ

where

J₀ = reverse leakage, A/cm²,

C = junction capacitance, F/cm²,

τ = decay time, s, and

kT/q = 26 mV at T = 300 K.

Good agreement was obtained between experiment and theory. The examined range was four orders of magnitude in leakage current.