Berlin 2012 – scientific programme

Parts | Days | Selection | Search | Updates | Downloads | Help

HL: Fachverband Halbleiterphysik

HL 44: Poster Session: Quantum Dots and Wires - Transport & Optical Properties

HL 44.15: Poster

Tuesday, March 27, 2012, 09:30–12:30, Poster D

Optical Phonons in InAs/AlAs Structures with InAs and AlAs Nanocrystals — •Evgeniya Sheremet¹, Alexander Milekhin², Alexander Kalagin², Alexander Toropov², and Dietrich R.T. Zahn¹ — ¹Semiconductor Physics, Chemnitz University of Technology, D-09107 Chemnitz, Germany — ²Institute of Semiconductor Physics, 630090 Novosibirsk, Russia

Layered InAs/AlAs structures with InAs and AlAs nanocrystals (NCs) formed by Stranski-Krastanov growth on (001)-oriented GaAs substrates were investigated by Raman spectroscopy. Selection rules for the optical phonons in the structures were studied in a backscattering geometry from planar (001) and cleaved (110) surfaces using a micro-Raman setup. Transverse and longitudinal optical (TO and LO) phonons as well as interface (IF) phonons were observed for InAs (AlAs) NCs in AlAs (InAs) matrices. Optical phonon frequencies of InAs (AlAs) NCs are upshifted (downshifted) compared to the ones of the corresponding bulk materials. These shifts result from compressive (tensile) built-in strain in the NCs. The frequencies of optical phonons were used to determine deformationtensor components. It was found that optical phonons of InAs NCs obey Raman scattering selection rules for a superlattice consisting of materias with zinc-blende structure. However the selection rules are weakened since all the optical phonon peaks were detected in forbidden geometries (z(x,x)z and y′(z,z)ȳ’, where x, z and y′ stand for [100], [001] and [110], respectively). Meanwhile, the selection rules for optical phonons of AlAs NCs are lifted. This effect can be caused by built-in strain and defects.