Contactless determination of the conductivity in semi-insulators

It is shown how isothermal relaxation current measurements on MISM or MISIM multilayer structures can be used to determine the specific conductivity of materials in the range of about 10−12 to 10−5 Ω−1 cm−1. Using a boxcar integrator for measuring the current–time signals, the proposed method is applied to investigate the properties of semi-insulating GaAs and of AgBr at room temperature. In accordance with the expectations in the case of semi-insulating GaAs with increasing voltages a perceptible carrier depletion in the bulk takes place. From the polarity dependence of the extraction effect conclusions can be drawn about the predominant conduction mechanism.