Browsing by Author "Hsieh, M. C."

Now showing 1 - 2 of 2

Compensation effect and differential capacitance analysis of electronic energy band structure in relaxed InAs quantum dots
(2010-09-15)
Chen, J. F.
;
Chen, Ross C. C.
;
Chiang, C. H.
;
Hsieh, M. C.
;
Chang, Y. C.
The use of a differential capacitance technique for analyzing the effect of strain relaxation on the electronic energy band structure in relaxed InAs self-assembled quantum dots (QDs) is presented. Strain relaxation is shown to induce a deep defect state and compensate the ionized impurity in the bottom GaAs layer, leading to a double depletion width and a long emission time. An expression of capacitance at different frequency and voltage is derived for analyzing the experimental data. It has been shown that the relationship between the low-frequency and high-frequency capacitances can be well explained by a Schottky depletion model with a compensated concentration in the bottom GaAs layer. A simple expression is presented to account for the modulation of the free electrons in the top GaAs layer. This capacitance analysis shows a long low-energy tail for the electron ground state, suggesting not very uniform strain relaxation. The results of this study illustrate a carrier compensation effect of the defect state on the electronic energy band structure near the QDs. (C) 2010 American Institute of Physics. [doi:10.1063/1.3467938]
Improving the photoluminescence properties of self-assembled InAs surface quantum dots by incorporation of antimony
(2011-08-15)
Chiang, C. H.
;
Wu, Y. H.
;
Hsieh, M. C.
;
Yang, C. H.
;
Wang, J. F.
This study investigates the effects of surfactant and segregation from InAs surface quantum dots (SQDs) by incorporating antimony (Sb) into the QD layers. The Sb surfactant effect extends planar growth and suppresses dot formation. Incorporating Sb can reduce the density of SQDs by more than two orders of magnitude. Photoluminescence (PL) reveals enhancement in the optical properties of InAs SQDs as the Sb beam equivalent pressure (BEP) increases. This improvement is caused by the segregation of Sb on the surface of SQDs, which reduces non-radiative recombination and suppresses carrier loss. The dark line at the SQDs surface in the transmission electron microscopic image suggests that the incorporated Sb probably segregates close to the surface of the SQDs. These results indicate a marked Sb segregation effect that can be exploited to improve the surface-sensitive properties of SQDs for biological sensing. Crown Copyright (C) 2011 Published by Elsevier B. V. All rights reserved.