Zinc oxide thin film transistors with Schottky source barriers

Schottky barrier field effect transistors (SB FETs) with Schottky source injection barrier contacts are fabricated using zinc oxide (ZnO) thin films deposited by pulsed laser deposition at room temperature. In these devices, we utilize a gold Schottky barrier for the source and an aluminum ohmic metal for the drain contacts. The transistors exhibit field effect mobilities as high as 0.1 cm2 V−1 s−1, a current on/off ratio of 105, and a low saturation voltage of 6 V. When using ohmic source and drain contacts, transistor characteristics are not observed. Furthermore, the devices’ transconductance- and capacitance–voltage characteristics show a transition in the dominant carrier injection mechanism at the source barrier from thermionic emission to tunneling at a gate bias of approximately 8 V. These results demonstrate the promise of the Schottky source barrier FET architecture for building ZnO-based transistors.

► We made ZnO SB TFTs by PLD using a Schottky source and an ohmic drain contact.
► We only observed transistor characteristics when using the Schottky source barrier.
► A transition in the current injection mechanism at a gate bias of 8 V was observed.
► How to get an enhancement-mode transistor using the SB TFT concept is discussed.