Browsing by Author "Nicholas, RJ"

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InGaAs/GaAs quantum wells and quantum dots on (111)B orientation
(2001)
Tyan, SL
;
Lin, YG
;
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
;
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.