Title: Electron and Phonon Dynamics in IIIV and IIVI Compound Crystals
1Electron 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
2R. 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?
3Cubic GaN
4InSb
Experiment Asauskas, R., Z. Dobrovolskis, and A.
Krotkus, Sov. Phys. Semicond. 14, 12 (1980)
1377-1380.
5CdTe 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).
6ZnTe
Electron and phonon response to 300 fs pulses
repeated each 10 ps
7Lattice temperature effects
8From particle to wave concept
THz chirp
9Conclusions
- 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
10References
- 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).