19 October 2006 A computational study of carbon nanotube optoelectronic devices
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Since the first demonstration of electroluminescence (EL) from a CNTFET about three year ago, significant progress has been achieved in CNT optoelectronics. We have developed semiclassical and quantum transport simulators for CNT optoelectronic devices. A self-consistent simulation, which couples a quantum treatment of the metal-CNT contacts to a semiclassical treatment of the channel, is performed to understand carrier transport and light emission in a CNT infrared emitter. The results show that when the channel is long, light emission significantly affects carrier transport, and reduces the source-drain current by a factor of 2 in ambipolar transport regime. The experimentally observed light-spot movement along the channel can be mostly understood and explained by a simple, semiclassical picture. The photoconductivity of carbon nanotube (CNT) Schottky barrier transistors is studied by solving the nonequilibrium Green's function transport equation. The model provides a detailed and coherent picture of electron-photon coupling and quantum transport effects. The photocurrent shows peaks at photon energies near the subband gaps, which can be engineered by controlling the CNT diameter. Electron-phonon coupling (i) slightly broadens the peaks, (ii) leads to phonon-assisted photocurrent at certain energy ranges, and (iii) changes the energy-resolved photocurrent. We also show that the metal/CNT barrier height has a much smaller effect on the photocurrent than on the dark current. We also show the important role of sub-bandgap impact ionization and excitation in CNT devices.
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Youngki Yoon, Youngki Yoon, Yijian Ouyang, Yijian Ouyang, Muhammad A. Alam, Muhammad A. Alam, Jing Guo, Jing Guo, } "A computational study of carbon nanotube optoelectronic devices", Proc. SPIE 6370, Nanomaterial Synthesis and Integration for Sensors, Electronics, Photonics, and Electro-Optics, 63700G (19 October 2006); doi: 10.1117/12.690714; https://doi.org/10.1117/12.690714

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