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Terahertz‐Frequency Intraband Absorption in Semiconductor Quantum Dot Molecules
Author(s) -
Boucaud P.,
Gill K.S.,
Williams J.B.,
Sherwin M.S.,
Schoenfeld W.V.,
Petroff P.M.
Publication year - 2001
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/1521-3951(200103)224:2<443::aid-pssb443>3.0.co;2-v
Subject(s) - quantum dot , antibonding molecular orbital , materials science , absorption (acoustics) , terahertz radiation , quantum dot laser , saturation (graph theory) , semiconductor , absorption band , excitation , optoelectronics , electron , molecular physics , chemistry , optics , physics , semiconductor laser theory , mathematics , quantum mechanics , combinatorics , atomic orbital , composite material
We have studied THz absorption of samples containing two layers of self‐aligned, self‐assembled InAs quantum dots separated by a thin GaAs barrier. The electronic population of the vertically‐coupled dots is controlled by an applied bias between a metal gate and a doped layer beneath the dots. Under flat band conditions, an absorption peak is observed near 10 meV (2.4 THz). The absorption is attributed to the intersublevel transition between the quantum mechanically split bonding and antibonding levels in the quantum dot molecules. This absorption can be bleached under high excitation intensity delivered by a free‐electron laser. The saturation intensity is found to be of order 1 W cm —2 . A lower limit for the relaxation time T 1 of the order of 30 ps is deduced from the saturation intensity.