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Spectroscopic Ellipsometry And Absorption Study Of Zn1-Xmnxo/Al2o3 (0 <= X <= 0.08) Thin Films, Ghil Soo Lee, Ho Suk Lee, Tae Dong Kang, Hosun Lee, C. Liu, B. Xiao, Ü. Özgür, H. Morkoç

Electrical and Computer Engineering Publications

We grow Zn1−xMnxO∕Al2O3 (0⩽x⩽0.08)thin films on sapphire (0001) using radio-frequency sputtering deposition method with Ar and various N2 flow rates. We examine the effect of N2 codoping on the band gap and Mn-related midgap absorption of (Zn,Mn)O. Using spectroscopic ellipsometry, we measure pseudodielectric functions in the spectral range between 1 and 4.5eV. Using the model of Holden et al. [T. Holden et al., Phys. Rev. B56, 4037 (1997)], we determine the uniaxial (Zn,Mn)O dielectric function and the E0 band-gapenergy. The fitted band gap does not change appreciably with increasing Mn composition up to 2%. We find a very large …

Illumination And Annealing Characteristics Of Two-Dimensional Electron Gas Systems In Metal-Organic Vapor-Phase Epitaxy Grown Alxga1-Xn/Aln/Gan Heterostructures, N. Biyikli, Ü. Özgür, X. Ni, Y. Fu, H. Morkoç, Ç. Kurdak

Electrical and Computer Engineering Publications

We studied the persistent photoconductivity (PPC) effect in AlxGa1−xN∕AlN∕GaN heterostructures with two different Al compositions (x=0.15and x=0.25). The two-dimensional electron gas formed at the AlN∕GaN heterointerface was characterized by Shubnikov-de Haas and Hall measurements. Using optical illumination, we were able to increase the carrier density of the Al0.15Ga0.85N∕AlN∕GaN sample from 1.6×1012 to 5.9×1012cm−2, while the electron mobility was enhanced from 9540 to 21400cm2/Vs at T=1.6K. The persistent photocurrent in both samples exhibited a strong dependence on illumination wavelength, being highest close to the band gap and decreasing at longer wavelengths. The PPC effect became fairly weak for illumination wavelengths longer …

Spin Relaxation In A Germanium Nanowire, S. Patibandla, S. Pramanik, S. Bandyopadhyay, G. C. Tepper

Electrical and Computer Engineering Publications

We report experimental study of spin transport in nanowirespin valve structures consisting of three layers—cobalt, germanium, and nickel. The spin diffusion length in the Ge is estimated to be about 400nm at 1.9K and the corresponding spin relaxation time is about 4ns. At 100K, the spin diffusion length drops to 180nm and the relaxation time is about 0.81ns. These short relaxation times, which depend weakly on temperature, are caused by strong surface roughness scattering that causes rapid spin relaxation via the Elliott-Yafet mode [Elliott, Phys. Rev.96, 266 (1954)].

Integrating Schedulability Analysis With Uml-Rt, Qimin Gao, Lyndon Brown, Luiz Fernando Capretz

Electrical and Computer Engineering Publications

The use of object oriented techniques and methodologies for the design of real-time control systems appear to be necessary in order to deal with the increasing complexity of such systems. Recently many object-oriented methods have been used for the modeling and design of real-time control systems. We believe that an approach that integrates the advancements in both object modeling and design methods, and real-time scheduling theory is the key to successful use of object oriented technology for real-time software. However, past approaches to integrate the two either restrict the object models, or do not allow sophisticated schedulability analysis techniques. In …