Electron and Phonon Dynamics in IIIV and IIVI Compound Crystals

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Electron and Phonon Dynamics in III-V and II-VI
Compound Crystals
COST 288 MC Meeting, Metz-SUPELEC, 26 March 2007

• R. Brazis
• in collaboration with R. Raguotis
• and PhD student D. Nausewicz
• Semiconductor Physics Institute
• Vilnius, Lithuania

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R. Brazis, COST 288 MC Meeting, Metz-SUPELEC, 26
March 2007
Introduction

• Leading questions
• Stimulated THz photon emission by lattice
  vibrations is it feasible?
• Build-up and decay does it fit fs and nm scale?

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Cubic GaN
4
InSb
Experiment Asauskas, R., Z. Dobrovolskis, and A.
Krotkus, Sov. Phys. Semicond. 14, 12 (1980)
1377-1380.
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CdTe and ZnTe
Fig. 1. Response of electron drift velocity, mean
energy, maximum value of phonon distribution
function and total phonon number to the step-like
switching-on electric field E5kV/cm, T10K.
n-ZnTe and n-CdTe. Fig. 2. Phonon distribution
along the longitudinal tube centered at qxqy0
and along the transverse tube centered at qz
/kLO 0.2 in momentum space E (0,0,E0), E0
5 kV/cm, T 10 K, kLO3.1978 ?108 m-1 (ZnTe) and
kLO2.3391?108 m-1 (CdTe).
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ZnTe
Electron and phonon response to 300 fs pulses
repeated each 10 ps
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Lattice temperature effects
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From particle to wave concept
THz chirp
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Conclusions

• LO phonon band population can be inverted
  relative to the LA phonon band at the same
  wavevector qkLO
• it is the necessary condition of stimulated
  emission of THz photons by lattice vibrations
• temperatures 10 K are needed for operation

• LO phonon distribution build-up time (fs scale)
  is limited by the free (ballistic) flight of
  electrons in electric field the time of decay is
  limited by phonon lifetime and by electron energy
  relaxation time (gtps scale).

• Further research questions
• What are photon-two-phonon coupling coefficient
  values?
• What is optimum diode and feedback?
• Wave concept of electrons fs transmission
  oscillations

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References

• Brazis R., Raguotis R., The influence of phonon
  emission on electron transport in hexagonal and
  cubic gallium nitride, Acta Phys. Pol. A, V.
  107, No. 2, p. 324-327 (2005). ISSN 0587-4246
• Brazis R., Raguotis R., Monte Carlo modeling of
  phonon-assisted carrier transport in cubic and
  hexagonal gallium nitride, Opt. Quantum Electr.
  38, 339347 (2006). ISSN 0306-8919.
• Brazis R., D. Nausewicz, and R. Raguotis, Phonon-
  and Electron-Related Far-Infrared Absorption in
  CdTe and ZnTe Crystals, physica status solidi
  (b), 2007 (to be published). ISSN 0370-1972
• Brazis R. and Nausewicz D., Far-Infrared Photon
  Absorption by Phonons in ZnTe Crystals, Optical
  Materials, Elsevier NH, 2007 (to be published).
  ISSN 0925-3467
• Brazis R., Raguotis R., Femtosecond switching of
  electron and phonon streams in gallium nitride
  crystals, ICTON - Proc. of the 8th Int. Conf. on
  Transparent Optical Networks, Nottingham, UK,
  June 1822, 2006, IEEE, Inc., 2006, vol. 2, p.
  203206. (ISBN 1-4244-0235-2, IEEE Catalog Number
  06EX1326, Library of Congress 2006921097).
• Brazis R., Raguotis R., Built-up of inverted
  phonon distribution in GaN, 28th International
  Conference on the Physics of Semiconductors,
  Vienna, Austria, 24-28 July, 2006 (AIP Conference
  Proceedings    Print ISSN 0094-243X    Online
  ISSN 1551-7616). (to be published).
• R. Brazis, R. Raguotis, Electron and Phonon
  Dynamics in Indium Antimonide Crystals, IPSSO
  2007 International Workshop on Instabilities,
  Patterns and Spatial Solitons, Metz, March 2007
  (conference digest).