Title: Comparative study of the pressure dependence of optical-phonon transverse-effective charges and linewidths in wurtzite InN

Abstract

In this work, we investigate the hydrostatic pressure dependence of the zone center optical phonons of $c$-plane and $a$-plane wurtzite InN epilayers grown on GaN substrates. The longitudinal to transverse mode splitting for the $A_1$ and $E_1$ modes was found to increase with increasing pressure, whereas the associated transverse effective charge decreases for both modes as $e_T^{*}\left(A_1\right)=2.93–9.9\times {10}^{-3}P$ and $e_T^{*}\left(E_1\right)=2.80–10.6\times {10}^{-3}P$ (in units of elementary charge and $P$ in GPa). These observations are well in line with results for other II–VI, III–V, and group-IV semiconductor compounds as far as the relation between the magnitude and sign of the pressure derivative of $e_T^{*}$ and the bond ionicity is concerned. As the latter increases so does $|\partial e_T^{*}/\partial P|$ with a sign change from positive to negative for bond ionicities around $f_i=0.46$ for compounds with anions belonging to the first row of the Periodic Table. A comparison of the results for InN and other nine tetrahedrally bonded compounds indicate that the pressure behavior of the transverse effective charge is mainly determined by the strength of the Pauli repulsion between cation valence electrons and those of the anion core. We also perform ab initio calculations in order to address the origin of the observed increase in linewidth of the $E_2^{\text{high}}$ mode which is found to arise from a pressure-induced increase in the rate of two-phonon decay processes. In conclusion, this broadening is associated with tuning into resonance of a steep edge in the two-phonon density of states around 460 ${\mathrm{cm}}^{-1}$ with the frequency of the $E_2^{\text{high}}$ mode.

Authors:

Reparaz, J. S. ^[1]; da Silva, K. Pereira ^[2]; Romero, A. H. ^[3]; Serrano, J. ^[4]; Wagner, M. R. ^[5]; Callsen, G. ^[5]; Choi, S. J. ^[6]; Speck, J. S. ^[6]; Goñi, A. R. ^[7]

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+ Show Author Affiliations

1. Inst. de Ciència de Materials de Barcelona-CSIC, Bellaterra (Spain)
2. Inst. de Ciència de Materials de Barcelona-CSIC, Bellaterra (Spain); Univ. Federal do Pará, Belém, Pará (Brazil)
3. West Virginia Univ., Morgantown, WV (United States); Benemérita Univ. Autónoma de Puebla, Puebla (Mexico)
4. Yachay Tech Univ., Urcuqu (Ecuador)
5. Technische Univ. Berlin (Germany)
6. Univ. of California, Santa Barbara, CA (United States)
7. Inst. de Ciència de Materials de Barcelona-CSIC, Bellaterra (Spain); Inst. Catalana de Recerca i Estudis Avançats (ICREA), Barcelona (Spain)

Publication Date:

Tue Oct 16 00:00:00 EDT 2018

Research Org.:

West Virginia Univ., Morgantown, WV (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF); Spanish Ministerio de Economía, Industria y Competitividad; US Air Force Office of Scientific Research (AFOSR); US Department of the Navy, Office of Naval Research (ONR)

OSTI Identifier:

1593996

Alternate Identifier(s):

OSTI ID: 1478561

Grant/Contract Number:  

SC0016176; SEV-2015-0496; OCI-1053575; MAT2015-70850-P; CSD2010-00044; MAT2017-90024-P; DMREF-NSF-1434897

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review B

Additional Journal Information:

Journal Volume: 98; Journal Issue: 16; Journal ID: ISSN 2469-9950

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY