Browsing by Author "Oruc, F. B."
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Item Open Access Dynamic control of photoresponse in ZnO-based thin-film transistors in the visible spectrum(IEEE, 2013-04) Aygun, L. E.; Oruc, F. B.; Atar, F. B.; Okyay, Ali KemalWe present ZnO-channel thin-film transistors with actively tunable photocurrent in the visible spectrum, although ZnO band edge is in the ultraviolet. ZnO channel is deposited by atomic layer deposition technique at a low temperature (80), which is known to introduce deep level traps within the forbidden band of ZnO. The gate bias dynamically modifies the occupancy probability of these trap states by controlling the depletion region in the ZnO channel. Unoccupied trap states enable the absorption of the photons with lower energies than the bandgap of ZnO. Photoresponse to visible light is controlled by the applied voltage bias at the gate terminal. © 2009-2012 IEEE.Item Open Access Low temperature atomic layer deposited ZnO photo thin film transistors(AVS Science and Technology Society, 2014) Oruc, F. B.; Aygun, L. E.; Donmez, I.; Bıyıklı, Necmi; Okyay, Ali Kemal; Yu, H. Y.ZnO thin film transistors (TFTs) are fabricated on Si substrates using atomic layer deposition technique. The growth temperature of ZnO channel layers are selected as 80, 100, 120, 130, and 250°C. Material characteristics of ZnO films are examined using x-ray photoelectron spectroscopy and x-ray diffraction methods. Stoichiometry analyses showed that the amount of both oxygen vacancies and interstitial zinc decrease with decreasing growth temperature. Electrical characteristics improve with decreasing growth temperature. Best results are obtained with ZnO channels deposited at 80°C; Ion/Ioff ratio is extracted as 7.8 × 109 and subthreshold slope is extracted as 0.116 V/dec. Flexible ZnO TFT devices are also fabricated using films grown at 80°C. ID-VGS characterization results showed that devices fabricated on different substrates (Si and polyethylene terephthalate) show similar electrical characteristics. Sub-bandgap photo sensing properties of ZnO based TFTs are investigated; it is shown that visible light absorption of ZnO based TFTs can be actively controlled by external gate bias. © 2014 American Vacuum Society.Item Open Access Thin-film ZnO charge-trapping memory cell grown in a single ALD step(Institute of Electrical and Electronics Engineers, 2012-10-26) Oruc, F. B.; Cimen, F.; Rizk, A.; Ghaffari, M.; Nayfeh, A.; Okyay, Ali KemalA thin-film ZnO-based single-transistor memory cell with a gate stack deposited in a single atomic layer deposition step is demonstrated. Thin-film ZnO is used as channel material and charge-trapping layer for the first time. The extracted mobility and subthreshold slope of the thin-film device are 23 cm2/V · s and 720 mV/dec, respectively. The memory effect is verified by a 2.35-V hysteresis in the $I\rm drain- $V\rm gate curve. Physics-based TCAD simulations show very good agreement with the experimental results providing insight to the charge-trapping physics.