Propagation of THz acoustic wave packets in GaN at room temperature

A. A. Maznev; T. C. Hung; Y. T. Yao; T. H. Chou; J. S. Gandhi; L. Lindsay; H. D. Shin; D. W. Stokes; R. L. Forrest; A. Bensaoula; C. K. Sun; K. A. Nelson

doi:10.1063/1.5008852

Propagation of THz acoustic wave packets in GaN at room temperature

A. A. Maznev, T. C. Hung, Y. T. Yao, T. H. Chou, J. S. Gandhi, L. Lindsay, H. D. Shin, D. W. Stokes, R. L. Forrest, A. Bensaoula, C. K. Sun, K. A. Nelson

Multiscale Modeling & Materials by Desig

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Abstract

We use femtosecond laser pulses to generate coherent longitudinal acoustic phonons at frequencies of 1-1.4 THz and study their propagation in GaN-based structures at room temperature. Two InGaN-GaN multiple-quantum-well (MQW) structures separated by a 2.3 μm-thick GaN spacer are used to simultaneously generate phonon wave packets with a central frequency determined by the period of the MQW and detect them after passing through the spacer. The measurements provide lower bounds for phonon lifetimes in GaN, which are still significantly lower than those from first principles predictions. The material Q-factor at 1 THz is found to be at least as high as 900. The measurements also demonstrate a partial specular reflection from the free surface of GaN at 1.4 THz. This work shows the potential of laser-based methods for THz range phonon spectroscopy and the promise for extending the viable frequency range of GaN-based acousto-electronic devices.

Original language	English
Article number	061903
Journal	Applied Physics Letters
Volume	112
Issue number	6
DOIs	https://doi.org/10.1063/1.5008852
State	Published - Feb 5 2018

Funding

The contribution by A.A.M., H.D.S., and K.A.N. was supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Award No. DE-FG02-00ER15087. The contribution by T.-C.H., Y.-T.Y., T.-H. C., and C.-K.S. was supported by the Taiwan Ministry of Science and Technology, MOST 106-2112-M-002-004-MY3. The contribution by J.S.G., D.W.S., R.L.F., and A.B. was supported by the University of Houston Grants to Enhance Research Program (Grant No. 55322). L.L. acknowledges support from the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division. STEM imaging was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility, at Oak Ridge National Laboratory. The contribution by J.S.G., D.W.S., R.L.F., and A.B. was supported by the University of Houston Grants to Enhance Research Program (Grant No. 55322). L.L. acknowledges support from the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division. STEM imaging was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility, at Oak Ridge National Laboratory.

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title = "Propagation of THz acoustic wave packets in GaN at room temperature",

abstract = "We use femtosecond laser pulses to generate coherent longitudinal acoustic phonons at frequencies of 1-1.4 THz and study their propagation in GaN-based structures at room temperature. Two InGaN-GaN multiple-quantum-well (MQW) structures separated by a 2.3 μm-thick GaN spacer are used to simultaneously generate phonon wave packets with a central frequency determined by the period of the MQW and detect them after passing through the spacer. The measurements provide lower bounds for phonon lifetimes in GaN, which are still significantly lower than those from first principles predictions. The material Q-factor at 1 THz is found to be at least as high as 900. The measurements also demonstrate a partial specular reflection from the free surface of GaN at 1.4 THz. This work shows the potential of laser-based methods for THz range phonon spectroscopy and the promise for extending the viable frequency range of GaN-based acousto-electronic devices.",

author = "Maznev, \{A. A.\} and Hung, \{T. C.\} and Yao, \{Y. T.\} and Chou, \{T. H.\} and Gandhi, \{J. S.\} and L. Lindsay and Shin, \{H. D.\} and Stokes, \{D. W.\} and Forrest, \{R. L.\} and A. Bensaoula and Sun, \{C. K.\} and Nelson, \{K. A.\}",

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doi = "10.1063/1.5008852",

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AU - Maznev, A. A.

AU - Hung, T. C.

AU - Yao, Y. T.

AU - Chou, T. H.

AU - Gandhi, J. S.

AU - Lindsay, L.

AU - Shin, H. D.

AU - Stokes, D. W.

AU - Forrest, R. L.

AU - Bensaoula, A.

AU - Sun, C. K.

AU - Nelson, K. A.

PY - 2018/2/5

Y1 - 2018/2/5

N2 - We use femtosecond laser pulses to generate coherent longitudinal acoustic phonons at frequencies of 1-1.4 THz and study their propagation in GaN-based structures at room temperature. Two InGaN-GaN multiple-quantum-well (MQW) structures separated by a 2.3 μm-thick GaN spacer are used to simultaneously generate phonon wave packets with a central frequency determined by the period of the MQW and detect them after passing through the spacer. The measurements provide lower bounds for phonon lifetimes in GaN, which are still significantly lower than those from first principles predictions. The material Q-factor at 1 THz is found to be at least as high as 900. The measurements also demonstrate a partial specular reflection from the free surface of GaN at 1.4 THz. This work shows the potential of laser-based methods for THz range phonon spectroscopy and the promise for extending the viable frequency range of GaN-based acousto-electronic devices.

AB - We use femtosecond laser pulses to generate coherent longitudinal acoustic phonons at frequencies of 1-1.4 THz and study their propagation in GaN-based structures at room temperature. Two InGaN-GaN multiple-quantum-well (MQW) structures separated by a 2.3 μm-thick GaN spacer are used to simultaneously generate phonon wave packets with a central frequency determined by the period of the MQW and detect them after passing through the spacer. The measurements provide lower bounds for phonon lifetimes in GaN, which are still significantly lower than those from first principles predictions. The material Q-factor at 1 THz is found to be at least as high as 900. The measurements also demonstrate a partial specular reflection from the free surface of GaN at 1.4 THz. This work shows the potential of laser-based methods for THz range phonon spectroscopy and the promise for extending the viable frequency range of GaN-based acousto-electronic devices.

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Propagation of THz acoustic wave packets in GaN at room temperature

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