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

被引：2

作者：

Mintairov, AM ^{[1
]}

Vlasov, AS ^{[1
]}

Merz, JL ^{[1
]}

Korakakis, D ^{[1
]}

Moustakas, TD ^{[1
]}

Osinsky, AO ^{[1
]}

Gaska, R ^{[1
]}

Smirnov, MB ^{[1
]}

机构：

[1] Univ Notre Dame, EE Dept, Notre Dame, IN 46556 USA

来源：

WIDE-BANDGAP SEMICONDUCTORS FOR HIGH-POWER, HIGH-FREQUENCY AND HIGH-TEMPERATURE APPLICATIONS-1999 | 1999年 / 572卷

关键词：

D O I：

10.1557/PROC-572-427

中图分类号：

T [工业技术];

学科分类号：

08 ;

摘要：

We report an experimental (infrared reflectance spectroscopy) and theoretical study of the polar optical phonons in hexagonal ternary nitride compounds: AlNm/GaNn (n=2-8, m=4, 8) superlattices (SL) and spontaneously ordered AlxGa1-xN (x=0.08-0.55) alloys. In infrared (IR) reflectivity spectra we revealed two modes having strong LO-TO splitting (20-150 cm(-1)), and several modes, having a small (1-3 cm(-1)) LO-TO splitting. All modes have a very high damping parameter greater than or equal to 20 cm(-1). The unusual observation is the negative value of the oscillator strength for the weak IR mode at similar to 690 cm(-1), suggesting possible lattice instability, consistent with high damping observed. We found from lattice dynamical calculations that weak IR active modes correspond to modes localized at GaN-AlN interfaces. Our 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 AIN. In SL samples the anomalous mode corresponds to phonons localized on interface inhomogenities.

引用

页码：427 / 432

页数：6

共 8 条

[1] INFRARED LATTICE VIBRATIONS AND DIELECTRIC DISPERSION IN CORUNDUM [J].