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Title: Disorder induced IR anomaly in hexagonal AlGaN short-period superlattices and alloys

Abstract

The authors report an experimental (infrared reflectance spectroscopy) and theoretical study of the polar optical phonons in hexagonal ternary nitride compounds: AlN{sub m}/GaN{sub n} (n = 2--8, m = 4, 8) superlattices (SL) and spontaneously ordered Al{sub x}Ga{sub 1{minus}x}N (x = 0.08--0.55) alloys. In infrared (IR) reflectivity spectra they revealed two modes having strong LO-TO splitting (20--150 cm{sup {minus}1}), and several modes, having a small (1--3 cm{sup {minus}1}) LO-TO splitting. All modes have a very high damping parameter {ge} 20 cm{sup {minus}1}. The unusual observation is the negative value of the oscillator strength for the weak IR mode at {approximately} 690 cm{sup {minus}1}, suggesting possible lattice instability, consistent with high damping observed. They found from lattice dynamical calculations that weak IR active modes correspond to modes localized at GaN-AlN interfaces. The analysis has shown that an anomalous mode is induced by the disorder effects and arises due to strong overlapping of the LO-TO phonon branches of the bulk GaN and AlN. In SL samples the anomalous mode corresponds to phonons localized on interface inhomogeneities.

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Univ. of Notre Dame, IN (US)
OSTI Identifier:
20104744
Resource Type:
Conference
Resource Relation:
Conference: 1999 Materials Research Society Spring Meeting, San Francisco, CA (US), 04/05/1999--04/08/1999; Other Information: PBD: 1999; Related Information: In: Wide-band semiconductors for high-power, high-frequency and high-temperature applications -- 1999. Materials Research Society symposium proceedings: Volume 572, by Binari, S.C.; Burk, A.A.; Melloch, M.R.; Nguyen, C. [eds.], 575 pages.
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; SUPERLATTICES; ORDER PARAMETERS; ALUMINIUM NITRIDES; GALLIUM NITRIDES; INFRARED SPECTRA; PHONONS

Citation Formats

Mintairov, A M, Vlasov, A S, Merz, J L, Korakakis, D, Moustakas, T D, Osinsky, A O, Gaska, R, and Smirnov, M B. Disorder induced IR anomaly in hexagonal AlGaN short-period superlattices and alloys. United States: N. p., 1999. Web.
Mintairov, A M, Vlasov, A S, Merz, J L, Korakakis, D, Moustakas, T D, Osinsky, A O, Gaska, R, & Smirnov, M B. Disorder induced IR anomaly in hexagonal AlGaN short-period superlattices and alloys. United States.
Mintairov, A M, Vlasov, A S, Merz, J L, Korakakis, D, Moustakas, T D, Osinsky, A O, Gaska, R, and Smirnov, M B. Thu . "Disorder induced IR anomaly in hexagonal AlGaN short-period superlattices and alloys". United States.
@article{osti_20104744,
title = {Disorder induced IR anomaly in hexagonal AlGaN short-period superlattices and alloys},
author = {Mintairov, A M and Vlasov, A S and Merz, J L and Korakakis, D and Moustakas, T D and Osinsky, A O and Gaska, R and Smirnov, M B},
abstractNote = {The authors report an experimental (infrared reflectance spectroscopy) and theoretical study of the polar optical phonons in hexagonal ternary nitride compounds: AlN{sub m}/GaN{sub n} (n = 2--8, m = 4, 8) superlattices (SL) and spontaneously ordered Al{sub x}Ga{sub 1{minus}x}N (x = 0.08--0.55) alloys. In infrared (IR) reflectivity spectra they revealed two modes having strong LO-TO splitting (20--150 cm{sup {minus}1}), and several modes, having a small (1--3 cm{sup {minus}1}) LO-TO splitting. All modes have a very high damping parameter {ge} 20 cm{sup {minus}1}. The unusual observation is the negative value of the oscillator strength for the weak IR mode at {approximately} 690 cm{sup {minus}1}, suggesting possible lattice instability, consistent with high damping observed. They found from lattice dynamical calculations that weak IR active modes correspond to modes localized at GaN-AlN interfaces. The analysis has shown that an anomalous mode is induced by the disorder effects and arises due to strong overlapping of the LO-TO phonon branches of the bulk GaN and AlN. In SL samples the anomalous mode corresponds to phonons localized on interface inhomogeneities.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1999},
month = {7}
}

Conference:
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