Transparent semiconducting oxides: materials and devices

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Abstract

Transparent conductive oxides (TCOs) are a well-known material class allowing Ohmic conduction. A large free carrier concentration in the 1021 cm−3 range and high conductivity (beyond 104 S/cm) is feasible simultaneously with high transparency. Applications are manifold and include touch screens and front contacts for displays or solar cells. Transparent semiconducting oxides (TSO) are oxides with an intermediate free carrier concentration (typically 1014–1018 cm−3) allowing the formation of depletion layers. We review recent results on TSO-based transistors and inverters. Most work has been reported on MISFETs. We show that MESFETs exhibit high performance and low voltage operation of oxide electronics. MESFET-based inverters offer superior performance compared to results reported for TSO MISFET-based circuits.

original image

Optical image of inverter based on thin film MESFETs with Mg0.003Zn0.997O channels (left) and experimental inverter characteristic for supply voltage of equation image (right).

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