High-performance Schottky diodes based on palladium blocking contacts were fabricated upon depositing indium-gallium-zinc oxide (IGZO) with high oxygen content. We find that an oxygen treatment of the palladium contact is needed to achieve low off currents in the Schottky diode, and rationalize this by relating an increased oxygen content at the Pd/IGZO interface to a lower interfacial trap density. Optimized IGZO films were obtained with a record high ratio of free charge carrier density to subgap traps. The rectification ratios of diodes with such films are higher than 107 with current densities exceeding 103 A/cm2 at low forward bias of 2 V.

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In this study, the authors report on high‐quality amorphous indium–gallium–zinc oxide thin‐film transistors (TFTs) based on a single‐source dual‐layer concept processed at temperatures down to 150°C. The dual‐layer concept allows the precise control of local charge carrier densities by varying the O2/Ar gas ratio during sputtering for the bottom and top layers. Therefore, extensive annealing steps after the deposition can be avoided. In addition, the dual‐layer concept is more robust against variation of the oxygen flow in the deposition chamber. The charge carrier density in the TFT channel is namely adjusted by varying the thickness of the two layers whereby the oxygen concentration during deposition is switched only between no oxygen for the bottom layer and very high concentration for the top layer. The dual‐layer TFTs are more stable under bias conditions in comparison with single‐layer TFTs processed at low temperatures. Finally, the applicability of this dual‐layer concept in logic circuitry such as 19‐stage ring oscillators and a TFT backplane on polyethylene naphthalate foil containing a quarter video graphics array active‐matrix organic light‐emitting diode display demonstrator is proven.

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High-performance Schottky diodes based on amorphous IGZO (Indium-Gallium-Zinc Oxide) semiconductor were fabricated and fully characterized. S-parameter measurements and subsequent analysis prove that these diodes have a cut-off frequency over 900MHz at 0V bias, making these diodes a promising choice for UHF applications, such as energy-harvesters for passive RFID tags on foil. Moreover, when used in a single stage rectifier, the diodes provide DC voltages higher than 1.2V at 900MHz, which is enough supply for circuitry on foil based on current metal-oxides technologies (1,2).

In this work, we report on high‐performance bottom‐gate top‐contact (BGTC) amorphous‐Indium‐Gallium‐Zinc‐Oxide (a‐IGZO) thin‐film transistor (TFT) with SiO2 as an etch‐stop‐layer (ESL) deposited by medium frequency physical vapor deposition (mf‐PVD). The TFTs show field‐effect mobility (μFE) of 16.0 cm2/(V.s), sub‐threshold slope (SS−1) of 0.23 V/decade and off‐currents (IOFF) < 1.0 pA. The TFTs with mf‐PVD SiO2 ESL deposited at room temperature were compared with TFTs made with the conventional plasma‐enhanced chemical vapor deposition (PECVD) SiO2 ESL deposited at 300 °C and at 200 °C. The TFTs with different ESLs showed a comparable performance regarding μFE, SS−1, and IOFF, however, significant differences were measured in gate bias‐stress stability when stressed under a gate field of +/−1 MV/cm for duration of 104 s. The TFTs with mf‐PVD SiO2 ESL showed lower threshold‐voltage (VTH) shifts compared with TFTs with 300 °C PECVD SiO2 ESL and TFTs with 200 °C PECVD SiO2 ESL. We associate the improved bias‐stress stability of the mf‐PVD SiO2 ESL TFTs to the low hydrogen content of the mf‐PVD SiO2 layer, which has been verified by Rutherford‐Back‐Scattering‐Elastic‐Recoil‐Detection technique.