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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/2897

Authors: Getnet, Melese
Advisors: Dr. S. K. Ghoshal
Keywords: Physics
Copyright: Jun-2009
Date Added: 10-May-2012
Publisher: AAU
Abstract: Bulk silicon (Si) and germanium (Ge) have an indirect band gap transitions; however when they are miniaturized to nanometeric scale, the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) increases, and hence the transition changes to direct due to confinement. The HOMO- LUMO gap determines the excitation of electrons so that the nanostructures will emit light. In this thesis, quantum confinement effects for Si and Ge, some methods of calculating band structures, comparative analysis of photoluminescence (PL) and electroluminescence (EL) are presented. The thesis focuses on EL and for comparison purpose, some studies on PL is touched. Both are the emission of energy in the form of light spectrum of different wavelength by optical radiation, and current or strong electric field. The dependence of EL on different parameters like size of the nanocluster, applied voltage, band gap energy, wavelength, temperature, and time for Si are briefly examined. The dielectric matrix silicon dioxide has unique optical and electrical properties, as a result the dependence of EL intensity on the above parameters for Si-terminated with oxygen and hydrogen is included in the thesis; in fact passivation enhances EL and highly efficient EL is obtained at low operating voltages (< 6V ), it is also observed that EL degrades with time. The EL and PL intensities occur at the same energy, however the EL intensity has sharp Gaussian peak and red shifted compared to the PL intensity. To get our result, we used the idea of quantum confinement model (QCM) and surface state model (SSM), that can explain PL and EL on pure Si nanostructures, and Si-terminated with impurities. Our results are consistent with experimental reports.
URI: http://hdl.handle.net/123456789/2897
Appears in:Thesis - Physics

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