Probing optical-phonon propagation in GaAs/Al{sub {ital x}}Ga{sub 1{minus}{ital x}}As quantum-well samples via their nonequilibrium population

Journal Article · Tue Oct 01 04:00:00 EDT 1996 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.54.10742· OSTI ID:389305

Yu, P Y; Su, Z ^[1]; Kim, D S; Khim, J S; Lim, Y S; Yee, Y H; Cho, Y H; Lee, J S; Lee, J H; Chang, J S; Choe, B D ^[2]; Woo, D H ^[3]; Shin, E J; Kim, D ^[4]; Arya, K ^[5]; Song, J J ^[6]

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1. Department of Physics, University of California, Berkeley, California 94720 (United States)
2. Department of Physics, Seoul National University, Seoul 151-742 (Korea)
3. Korea Institute of Science and Technology, Cheongryang, Seoul 136-791 (Korea)
4. Spectroscopy Laboratory, Korea Research Institute of Standard and Science, Taejon, 305-606 (Korea)
5. Department of Physics, California State University, San Jose, California 95192 (United States)
6. Department of Physics and Center for Laser Research, Oklahoma State University, Stillwater, Oklahoma 74078 (United States)

We develop a theoretical model to analyze a nonequilibrium optical- (LO-) phonon population by Raman scattering in GaAs/Al{sub {ital x}}Ga{sub 1{minus}{ital x}}As quantum wells. With the assumption of bulklike hot-electron relaxation, the effect of LO-phonon confinement on a nonequilibrium optical-phonon population (NOP) is isolated. Our analysis shows that the decrease in spatial extent or coherence length of LO phonons is reflected by a decrease in NOP. This is because the contributions from large {ital q} wave vectors with small occupation numbers dominate as the spatial extent decreases. Our method is applied to explain picosecond Raman-scattering experiments on GaAs/Al{sub {ital x}}Ga{sub 1{minus}{ital x}}As. The increasing NOP with decreasing {ital x} is interpreted as the result of an increase in the coherence length of LO phonons, since for smaller {ital x}, the Al{sub {ital x}}Ga{sub 1{minus}{ital x}}As barrier is no longer effective in localizing GaAs LO phonons within the well. Using this model, we also deduce coherence length of LO phonons as a function of {ital x}. Our results show that for values of {ital x} between 0.2 and 0.4, the GaAs LO phonon in GaAs/Al{sub {ital x}}Ga{sub 1{minus}{ital x}}As quantum wells changes from a bulklike propagating mode to one localized within the wells. {copyright} {ital 1996 The American Physical Society.}

• Research Organization: Lawrence Berkeley National Laboratory
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 389305
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 15 Vol. 54; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
66 PHYSICS
ALUMINIUM ARSENIDES
COHERENCE LENGTH
GALLIUM ARSENIDES
NONEQUILIBRIUM
PHONONS
PS RANGE
QUANTUM WELLS
RAMAN SPECTRA
RELAXATION TIME
SEMICONDUCTOR JUNCTIONS
SUBSTITUTION