A direct gate field-effect transistor for the measurement of DC electric fields

A solid-state dc field sensor based on MOS technology has been fabricated and tested. The device\´s key feature is the absence of a metalized gate electrode, i.e., the oxide layer and substrate channel beneath are exposed directly to the external field to be measured, which in turn modulates the channel current. Field to current "transconductance" on the order of 0.06 µA/kV/m has been observed. The screening of the field from the substrate surface, as charges flow over oxide layer leakage paths, occurs with a relaxation time on the order of 35 h with the device in air at room temperature.