A study of nanowire transistors and their applications for flexible and transparent electronics
Abstract
Development of optically transparent and mechanically flexible electronic circuitry represents an enabling step toward next-generation display technologies, including “see-through” and conformable products. Nanowire transistors (NWTs) are of particular interest for future display devices because of their high carrier mobilities compared with thin film transistors, the prospect of processing at low temperatures compatible with plastic substrates, as well as their optical transparency and inherent mechanical flexibility. In 2O3, ZnO, SnO2 and Ge nanowires are particularly promising candidates for transistor channels that satisfy these requirements because they are both transparent and mechanically robust/flexible. In addition to transparency, excellent transistor performance metrics such as on-current, on/off current ratio, mobility, subthreshold slope and threshold voltage are required for such devices, so that driving and switching transistors using nanowires can be assembled into useful electronic circuits. In this thesis, fully transparent nanowire transistor active-matrix organic light-emitting diodes (NW-AMOLED) display elements which contain 300 pixels were demonstrated. The drive circuitry for each 55 μm x 175 μm pixel consists of 1 switching nanowire transistor (NWT), 2 driving NWTs and 1 storage capacitor. The display region exhibits an optical transmittance of ∼72% and a green peak luminance of ∼300 cd/m2. The transparency of the entire pixel area should significantly enhance aperture ratio efficiency in active-matrix arrays and thus substantially decrease power consumption. Several key processes to build the NWTs on several gate insulators were developed and demonstrated with surface treatment and electrical aging which were performed to NWTs to improve the output characteristics. The reliability of NWTs in terms of proton radiation, bias stress, temperature and low-frequency noise measurements, along with current-voltage (I-V) characteristics were also investigated. These techniques can be used for the logic technologies, future space-based applications in electronics and future flexible and transparent OLED displays.
Degree
Ph.D.
Advisors
Janes, Purdue University.
Subject Area
Electrical engineering
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