Transistor action based on field-effect controlled current injection into an insulator/SrTiO3 interface

Transistor action with both voltage and current gain exceeding 1 was observed in structures consisting of metal electrodes, insulating barriers, and high-dielectric-constant insulating SrTiO3. These structures were made on insulating (100) single-crystal SrTiO3 substrates having a dielectric constant of 2×104 at 4.2 K. A Nb emitter and collector electrodes were placed on the substrates, with Si or SiO2 barriers between the emitter and substrate. Base leads were made with silver paste on the back of the SrTiO3 wafers. Devices both with and without barrier layers between the collector and substrate showed transistor action at 4.2 K. Essentially no current was required to control the collector current, which ranges from a few microamperes to a few milliamperes. For devices with a 30-μm-diam circular emitter having a minimum emitter-collector spacing of 15 μm, the voltage gain was 2.5–4 and the maximum transconductance 1.4 mS.