Highly enhanced second-order nonlinear susceptibilities in tailored GaN–AlGaN–AlN quantum well structures

✍ Scribed by A. Rostami; H. Baghban Asghari Nejad; H. Rasooli Saghai

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 769 KB
• Volume: 403
• Category: Article
• ISSN: 0921-4526
• DOI: 10.1016/j.physb.2008.02.004

✦ Synopsis

A tailoring proposal for design of the strained quantum well structures, optimized with respect to the intersubband resonant secondorder nonlinear properties, is presented in this article. A genetic-algorithm-based method is used in order to obtain the optimal potential shape, doping concentration and location in strained GaN-AlGaN-AlN quantum wells, and the structures are analyzed by a numerical solution of the Schro¨dinger-Poisson self-consistent method. In general form two types of asymmetric structures with remarkable results are obtained with different resonant frequencies, and in both cases results show a considerably high enhancement in the magnitude of the second-order nonlinear susceptibilities in higher resonant frequencies in comparison with a single quantum well structure with the same well width (5.02 Â 10 À8 m/V at _o ¼ 0:41 eVto 2.9 Â 10 À5 m/V at _o ¼ 0:44 eVand 2.43 Â 10 À5 m/V at _o ¼ 0:604 eV). The optimized structures exhibit considerable absorption coefficient and electroabsorption properties due to high dipole transition matrix element, high dopant concentration and reasonable Fermi level.