Browsing by Author "Lu, Shu-Kai"

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Size-dependent strain relaxation in InN islands grown on GaN by metalorganic chemical vapor deposition
(2009-02-09)
Tsai, Wen-Che
;
Lin, Feng-Yi
;
Ke, Wen-Cheng
;
Lu, Shu-Kai
;
Cheng, Shun-Jen
We report Raman measurements on InN islands grown on GaN by metalorganic chemical vapor deposition. The Raman frequency of the InN E(2) mode is found to decrease exponentially with the island's aspect ratio, indicating a size dependent strain relaxation during the island formation. Our results suggest that most of the strain at the InN-GaN interface have been released plastically during the initial stage of island formations. After that, the residual strain of only -3.5x10(-3) is further relaxed elastically via surface islanding. The experimental data are in agreement with the strain relaxation predicted from a simplified model analysis as well as three-dimensional finite-element simulations.
Tailoring of the Wave Function Overlaps InAs/GaAs(1-x)Sb(x) Type-II Quantum Dots
(2010-09-01)
Hsu, Wei-Ting
;
Liao, Yu-An
;
Lu, Shu-Kai
;
Cheng, Shun-Jen
;
Chiu, Pei-Chin
Effects of thermal annealing on the emission properties of type-II InAs quantum dots (QDs) covered by a thin GaAs(1-x)Sb(x) layer are investigated by photoluminescence (PL) and time-resolved PL measurements. Apart from large blueshifts and a pronounced narrowing of the QD emission peak, the annealing induced alloy intermixing also leads to enhanced radiative recombination rates and reduced localized states in the GaAs(1-x)Sb(x) layer. We find that the type-II QD structure can sustain thermal annealing up, to 850 degrees C. In particular, we find that it is possible to manipulate between type-I and type-II recombinations in annealed QDs by using different excitation powers. We demonstrate that postgrowth thermal annealing can be used to tailor the band alignment, the wave function overlaps, and hence the recombination dynamics in the InAs/GaAs(1-x)Sb(x) type-II QDs. (C) 2009 Elsevier B.V. All rights reserved.
Tailoring of the Wave Function Overlaps InAs/GaAs1-xSbx Type-II Quantum Dots
(2010-09-01)
Hsu, Wei-Ting
;
Liao, Yu-An
;
Lu, Shu-Kai
;
Cheng, Shun-Jen
;
Chiu, Pei-Chin
Effects of thermal annealing on the emission properties of type-II InAs quantum dots (QDs) covered by a thin GaAs1-xSbx layer are investigated by photoluminescence (PL) and time-resolved PL measurements. Apart from large blueshifts and a pronounced narrowing of the QD emission peak, the annealing induced alloy intermixing also leads to enhanced radiative recombination rates and reduced localized states in the GaAs1-xSbx layer. We find that the type-II QD structure can sustain thermal annealing up, to 850 degrees C. In particular, we find that it is possible to manipulate between type-I and type-II recombinations in annealed QDs by using different excitation powers. We demonstrate that postgrowth thermal annealing can be used to tailor the band alignment, the wave function overlaps, and hence the recombination dynamics in the InAs/GaAs1-xSbx type-II QDs. (C) 2009 Elsevier B.V. All rights reserved.