Inversion layer makes ZnO TFT best yet

The University of Alberta has use bipolar conduction to improve power handling in thin-film transistors (TFTs) – using electrons and holes instead of just one of them as mosfets do.

Tunnelling TFT U of Alberta 640

Their first breakthrough was forming an inversion hole layer in a wide-bandgap semiconductor, which has been a great challenge in the solid-state electronics field, according to the university.

Once this was achieved, “we were able to construct a unique combination of semiconductor and insulating layers that allowed us to inject holes at the MOS interface,” said engineer Gem Shoute.

Adding holes at the interface increased the chances of electron tunnelling across the dielectric barrier, allowing the transistor behave more like a bipolar transistor.

“Usually tunnelling current is considered a bad thing in mosfets and it contributes to unnecessary loss of power,” said Shoute. “What we’ve done is build a transistor that considers tunnelling current a benefit.”

“It’s actually the best-performing [TFT] device of its kind, ever,” said Professor Ken Cadien. “This kind of device is normally limited by the non-crystalline nature of the material that they are made of.”

The semiconductor is ZnO, with an HFO2 insulator (see diagram).

The University claims the device can be scaled, and can handle 10x more power than commercial thin film transistors.

A full description, which is worth a look, is available free from Nature Communications as: Sustained hole inversion layer in a wide-bandgap metal-oxide semiconductor with enhanced tunnel current.

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