Peter Jerome Cowdery-Corvan

Stable ZnO thin film transistors by fast open air atomic layer deposition

We report stable, high performance zinc oxide thin film transistors grown by an atmospheric pressure atomic layer deposition system. With all deposition and processing steps kept at or below 200°C, the alumina gate dielectric shows low leakage (below 10−8A∕cm2) and high breakdown fields. Zinc oxide thin film transistors in a bottom gate geometry yield on/off ratios above 108, near zero turn-on voltage, little or no hysteresis, and mobility greater than 10cm2∕Vs. With alumina passivation, shifts in threshold voltage under gate bias stress compare favorably to those reported in the literature.We report stable, high performance zinc oxide thin film transistors grown by an atmospheric pressure atomic layer deposition system. With all deposition and processing steps kept at or below 200°C, the alumina gate dielectric shows low leakage (below 10−8A∕cm2) and high breakdown fields. Zinc oxide thin film transistors in a bottom gate geometry yield on/off ratios above 108, near zero turn-on voltage, little or no hysteresis, and mobility greater than 10cm2∕Vs. With alumina passivation, shifts in threshold voltage under gate bias stress compare favorably to those reported in the literature.

ZnO Thin-Film Transistor Ring Oscillators with 31-ns Propagation Delay

We have fabricated ring oscillators (ROs) using ZnO thin films deposited by using a spatial atomic layer deposition process at atmospheric pressure and low temperature (200degC). Bottom-gate thin-film transistors with aluminum source and drain contacts were fabricated with a field-effect mobility of > 15 cm2/V ldr s. Seven-stage ROs operated at a frequency as high as 2.3 MHz for a supply voltage of 25 V, corresponding to a propagation delay of 31 ns/stage. These circuits also had propagation delays of ~100 ns/stage at a supply voltage of 15 V. To the best of our knowledge, these are the fastest ZnO circuits reported to date.

ZnO Thin Film Transistor Ring Oscillators with sub 75 nsec Propagation Delay

We have fabricated simple circuits, including ring oscillators, using ZnO thin films deposited by low temperature (200degC) atmospheric pressure chemical vapor deposition. Bottom gate TFTs with aluminum source and drain contacts typically had field effect mobility >15 cm2/Vs. Seven stage ring oscillators operated at frequency as high as 1 MHz for a supply voltage of 32 V, corresponding to a propagation delay less than 75 nsec/stage. These circuits also had propagation delay less than 150 ns/stage at a supply voltage of 18 V. To our knowledge, these are the fastest ZnO circuits reported to date.

Fast ZnO Thin-Film Transistor Circuits

We report here five-stage ring-oscillator-integrated circuits fabricated using ZnO TFTs with signal propagation delays as low as 100 ns (>1 MHz oscillation frequency) for a 45 V supply voltage. These circuits also operate at a supply voltage as low as 10 V. To our knowledge, these are the fastest ZnO integrated circuits reported to date. We also designed ring oscillators with different source/gate and drain/gate overlap to investigate aspects of the circuit speed.

Uniform ZnO Thin-Film Transistors by an Ambient Process

We have fabricated zinc oxide thin-film transistors using a novel ambient deposition process, with maximum temperature of 200degC. The TFTs deposited this way show sufficiently good properties to make them potentially applicable to OLED display backplanes.

P-196L: Late-News Poster: High-Performance Zinc Oxide Transistors by an Ambient Process

An ambient process was developed for producing both the dielectric and semiconductor layers of a zinc oxide-based thin-film transistor. The dielectric films exhibited good electrical properties, leading to devices with gate leakage less than 25 nA/cm2. Typical devices had mobilities in excess of 5 cm2/Vs from a process with a maximum substrate temperature of 200°C. In addition, devices showed reasonable electrical stability in this novel deposition process for dielectrics and semiconductors.