Browsing by Author "Chiu, Pei-Chin"

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Band alignment tuning of InAs quantum dots with a thin AlGaAsSb capping layer
(2013-04-29)
Liao, Yu-An
;
Hsu, Wei-Ting
;
Huang, Shih-Han
;
Chiu, Pei-Chin
;
Chyi, Jen-Inn
We investigate the optical properties of InAs quantum dots (QDs) capped with a thin AlxGa1-xAsSb layer. As evidenced from power-dependent and time-resolved photoluminescence (PL) measurements, the GaAsSb-capped QDs with type-II band alignment can be changed to type-I by adding Al into the GaAsSb capping layer. The evolution of band alignment with the Al content in the AlGaAsSb capping layer has also been confirmed by theoretical calculations based on 8-band k . p model. The PL thermal stability and the room temperature PL efficiency are also improved by AlGaAsSb capping. We demonstrate that using the quaternary AlGaAsSb can take the advantages of GaAsSb capping layer on the InAs QDs while retaining a type-I band alignment for applications in long-wavelength light emitters. (C) 2013 AIP Publishing LLC.
Carrier dynamics of type-II InAs/GaAs quantum dots covered by a thin GaAs(1-x)Sb(x) layer
(2008-07-21)
Chang, Wen-Hao
;
Liao, Yu-An
;
Hsu, Wei-Ting
;
Lee, Ming-Chih
;
Chiu, Pei-Chin
Carrier dynamics of InAs/GaAs quantum dots (QDs) covered by a thin GaAs(1-x)Sb(x) layer were investigated by time-resolved photoluminescence (PL). Both the power dependence of PL peak shift and the long decay time constants confirm the type-II band alignment at the GaAsSb-InAs interface. Different recombination paths have been clarified by temperature dependent measurements. At lower temperatures, the long-range recombination between the QD electrons and the holes trapped by localized states in the GaAsSb layer is important, resulting in a non-single-exponential decay. At higher temperatures, optical transitions are dominated by the short-range recombination with the holes confined to the band-bending region surrounding the QDs. (C) 2008 American Institute of Physics.
Effects of GaAsSb capping layer thickness on the optical properties of InAs quantum dots
(2011-08-15)
Hsu, Wei-Ting
;
Liao, Yu-An
;
Hsu, Feng-Chang
;
Chiu, Pei-Chin
;
Chyi, Jen-Inn
The optical properties of GaAsSb-capped InAs quantum dots (QDs) with different capping layer thickness are investigated. Both the emission energy and the recombination lifetime are found to be correlated with the capping layer thicknesses. Theoretical calculations indicate that the quantum confinement and the wave function distribution of hole states are sensitive to the GaAsSb capping layer thickness. The Sb induced change in QD size also plays a role in the optical properties of GaAsSb-capped QDs. Controlling the GaAsSb capping layer thickness is a feasible way to tailor the InAs QDs for long-wavelength applications. (C) 2011 American Institute of Physics. [doi:10.1063/1.3624464]
Effects of thermal annealing on the emission properties of type-II InAs/GaAsSb quantum dots
(2009-02-02)
Liao, Yu-An
;
Hsu, Wei-Ting
;
Chiu, Pei-Chin
;
Chyi, Jen-Inn
;
Chang, Wen-Hao
We report the 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. 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 GaAsSb layer. Evidences of the evolution from type-II to type-I band alignments are obtained from time-resolved and power-dependent photoluminescence measurements. 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/GaAsSb type-II QDs.
Enhanced normal-incident absorption of quantum-dot infrared photodetectors with smaller quantum dots
(2008-07-01)
Tseng, Chi-Che
;
Chou, Shu-Ting
;
Chen, Yi-Hao
;
Chen, Cheng-Nan
;
Lin, Wei-Hsun
Ten-period InAs-GaAs quantum-dot (QD) infrared photodetectors grown under different In adatom supply procedures are investigated. Two In adatom supply procedures of In shutter 1) always opened and 2) periodically opened/closed are adopted in this letter. Larger QD sizes in both height and diameter and more uniform size distribution are observed for samples grown under an In shutter periodically opened/closed condition. The device with QDs grown under the In shutter always opened condition has revealed shorter detection wavelengths and enhanced normal incident absorption. The phenomenon shows that beside the increase of energy difference between confinement states, smaller QD sizes would also enhance the normal incident absorption predicted for the theoretically zero-dimensional QD structures.
Enhancing luminescence efficiency of InAs quantum dots at 1.5 mu m using a carrier blocking layer
(2006-07-31)
Hsieh, Tung-Po
;
Chiu, Pei-Chin
;
Chyi, Jen-Inn
;
Chang, Hsiang-Szu
;
Chen, Wen-Yen
The authors report an effective way to enhance the optical efficiency of InAs quantum dots (QDs) on GaAs emitting at the wavelength of 1.5 mu m. It is found that the loss of holes from QDs to their proximity via the high indium composition InGaAs overgrown layer, which is necessary for achieving long wavelength emission, is the origin of photoluminescence intensity degradation at high temperature. Inserting a 4 nm thick Al0.45Ga0.55As layer, acting as a carrier blocking layer, into the GaAs capping matrix can improve the room temperature photoluminescence peak intensity by five and two times for the ground and first excited states, respectively.
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.
Time-resolved photoluminescence of type-II InAs/GaAs quantum dots covered by a thin GaAs(1-x)Sb(x) layer
(2009)
Liao, Yu-An
;
Hsu, Wei-Ting
;
Lee, Ming-Chih
;
Chiu, Pei-Chin
;
Chyi, Jen-Inn
We investigate carrier lifetimes of InAs/GaAs quantum dots (QDs) covered by a thin GaAs(1-x)Sb(x) layer by time-resolved photoluminescence (PL). Both the power dependent PL peak shift and the longer decay time confirm the type-II band alignments. Different recombination paths have been identified by temperature dependent measurements. At low temperatures, the long-range recombination with holes trapped in the GaAsSb layer is significant, resulting in non-single-exponential decays. The short-range recombination with holes confined in the band-bending region surrounding the InAs QDs is important at higher temperatures. The variation in decay time across the ground-state and the temporal PL peak redshift further confirm the localization of holes in the GaAsSb layer. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim