Browsing by Author "Tsai, FY"

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Exciton relaxation in Ga1-xInxAs/GaAs self-organized quantum dots
(1999-01-01)
Shen, JX
;
Oka, Y
;
Cheng, HH
;
Tsai, FY
;
Lee, CP
The exciton dynamics in Ga1-xInxAs/GaAs self-organized quantum dots grown on GaAs (1 1 1)B substrates are studied by the time-resolved photoluminescence (PL). We have found the intra-dot exciton relaxation by the reduction of the linewidth and peak energy and also by the energy-dependent PL rise time in the transient PL spectra. Compared with the energy relaxation in the reference quantum wells, we have confirmed that the exciton relaxation in three-dimensionally confined quantum dots is slower than in the quantum wells, (C) 1999 Academic Press.
InGaAs/GaAs quantum dots on (111)B GaAs substrates
(1998-09-01)
Tsai, FY
;
Lee, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
InGaAs/GaAs quantum dots have been grown directly on (111) B GaAs substrates using molecular beam epitaxy. The island growth mode, which causes quantum dot formation, is due to the 2X2 surface reconstruction as the growth temperature is lowered. It is not related to the Stranski-Krastanov growth mechanism because the nominal thickness of InGaAs used is far below the critical thickness and no wetting layer is found. Atomic force microscope images indicate island formation with the growth temperature below 480 degrees C. The photoluminescence (PL) spectra of quantum dots show large peak shifts compared with the reference quantum well of the same nominal thickness of InGaAs. The PL emission from the quantum dots is strong and the peaks are narrow. A linewidth as low as 8.5 meV at 8 K has been measured, indicating excellent quality. (C) 1998 American Institute of Physics. [S0021-8979(98)05017-8].
InGaAs/GaAs quantum wells and quantum dots on (111)B orientation
(2001)
Tyan, SL
;
Lin, YG
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Tsai, FY
;
Lee, CP
;
Shields, PA
We report a magneto optical characterization of InGaAs/GaAs quantum well (QW) and quantum dot (QD) structures grown on (111)B GaAs substrates. The photoluminescence (PL) peak shift under high excitation intensity is used to distinguish QW from QD structures together with atomic force microscopy (AFM) imaging, The binding energy in(lll)InGaAs/GaAs QW is about 5 meV, The extent of the wave function obtained from the diamagnetic shift of the PL peak energy is consistent with the result calculated by the k,p method. The InGaAs/GaAs QD lateral confinement energy and the dot size are also estimated from the diamagnetic shift of the PL lines. The lateral confinement energy is estimated as 7 meV. The mean radius of the InGaAs QD is about 14 nm and the dot height is about 6 nm, which is in good agreement with the results as revealed in AFM imaging. (C) 2001 Published by Elsevier Science Ltd.
Magneto-luminescence of quasi-zero dimensional In0.25Ga0.75As/GaAs quantum dots
(1998-12-01)
Cheng, HH
;
Nicholas, RJ
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Priest, A
;
Tsai, FY
;
Lee, CP
We report photoluminescence measurements on In0.25Ga0.75As/GaAs quantum well and dots grown on (1 1 1)B GaAs substrate in high magnetic fields up to 45 Tesla. A well-defined PL line with full width at half maximum of approximately 5.5 meV is observed. From an analysis of the zero field transition energy, we point out the importance of an internal piezoelectric field. By analyzing the diamagnetic shift of the PL in both Faraday and Voigt configurations, the optical characteristics of a quasi-zero dimensional exciton are discussed. (C) 1998 Elsevier Science B.V. All rights reserved.
Magneto-photoluminescence study of InGaAs/GaAs quantum wells and quantum dots grown on (111)B GaAs substrate
(2000-06-01)
Tyan, SL
;
Shields, PA
;
Nicholas, RJ
;
Tsai, FY
;
Lee, CP
InGaAs/GaAs quantum well (QW) and quantum dot (QD) structures grown on GaAs (111)B substrates under different growing temperatures are investigated by magneto-photoluminescence (PL) up to 15 T in both Faraday and Voigt configurations. The spatial extents of the carrier wave functions (ECWFs) are deduced from the diamagnetic shift of the PL peak energy. The binding energies of the InGaAs/GaAs QWs are evaluated to be about 5 meV. The QW ECWFs in the growth direction obtained by the diamagnetic shift are consistent with those calculated by the k . p theory. The heights and radii of the InGaAs/GaAs QDs are also estimated from the ECWFs. In addition, we found that the in-plane ECWFs decreased slightly as the growth temperature was varied from 525 to 450 degrees C. The ECWFs in the growth direction decreased when the growth temperature was varied from 525 to 480 degrees C and then increased as the temperature was decreased to 450 degrees C.
Photoluminescence study of high-quality InGaAs/GaAs quantum dots on (111)B GaAs substrates
(1999-01-01)
Tsai, FY
;
Lee, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We present a simple in situ method to fabricate high-quality InGaAs/GaAs quantum dots on (111)B GaAs substrates. The mechanism of the quantum dot formation is not strain relaxation but the growth characteristic of (111)B GaAs under low substrate temperatures. When the growth is performed at low temperatures, the layer-by-layer growth mode is replaced by island growth and therefore quantum dots are formed. The formation of the quantum dots was verified by atomic force microscope (AFM) images and the shift of photoluminescence (PL). The PL emission from the quantum dots was very strong and the full-width at half-maximum (FWHM) of the emission peak was as small as 7.7 meV, indicating excellent quality and very uniform dot formation. The effect of nominal thickness on the quantum dot formation has been investigated.
Time-resolved photoluminescence study of InGaAs/GaAs quantum wells on (111)B GaAs substrates
(1999-04-01)
Tsai, FY
;
Lee, CP
;
Shen, JX
;
Oka, Y
;
Cheng, HH
The exciton dynamics in In0.15Ga0.85As/GaAs quantum wells grown on (111)B and (100)GaAs substrates are studied by the time-resolved photoluminescence (PL). We have found that the piezoelectric fields in (111)B samples affect the transient behavior of PL spectra. Compared with the reference (100) samples, we have confirmed that the piezoelectric effect induces slower exciton relaxation in (111)B strained quantum wells. (C) 1999 Elsevier Science Ltd. All rights reserved.
Time-resolved photoluminescence study of InGaAs/GaAs quantum wells on (111)B GaAs substrates under magnetic fields
(2001-06-15)
Tsai, FY
;
Lee, CP
;
Voskoboynikov, O
;
Cheng, HH
;
Shen, JX
The exciton dynamics in InxGa1-xAs/GaAs quantum wells grown on (111)B and (100) GaAs substrates were studied by time-resolved photoluminescence (PL) under magnetic fields in a Faraday configuration. We have found that the piezoelectric fields in (111)B samples affect the transient behavior of the PL spectra. Compared with the reference (100) sample, we have found that the strong piezoelectric fields, as well as the magnetic fields, cause a slower spin-flip process in (111)B strained quantum wells. (C) 2001 American Institute of Physics.