Browsing by Author "Liao, Yu-An"

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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.
In-Plane Gate Transistors for Photodetector Applications
(2013-06-01)
Liao, Yu-An
;
Lin, Wei-Hsun
;
Chao, Yi-Kai
;
Chang, Wen-Hao
;
Chyi, Jen-Inn
In-plane gate transistors (IPGTs) with 20-mu m channel widths are fabricated on samples with n-(InGa)As sheet resistance embedded in undoped GaAs matrix. A trade-off between effective current modulation and high saturation drain current is obtained by optimizing the doping density of the sheet resistance. The mechanism responsible for the transistor behaviors of the devices is due to the channel electron depletion related to the population of mobile surface electrons under different gate biases. The photocurrent measurements demonstrate that the IPGT architecture is a feasible approach for the applications of photodetectors.
Memory device application of wide-channel in-plane gate transistors with type-II GaAsSb-capped InAs quantum dots
(2013-09-30)
Liao, Yu-An
;
Chao, Yi-Kai
;
Chang, Shu-Wei
;
Chang, Wen-Hao
;
Chyi, Jen-Inn
We demonstrate room-temperature electron charging/discharging phenomena of InAs quantum dots using wide-channel in-plane gate transistors. The device based on type-II GaAsSb-capped InAs quantum dots exhibits both the longer charging and discharging times than those of the type-I counterpart with GaAs capping layers. The slow charge relaxation of GaAsSb-capped InAs quantum dots and simple architecture of in-plane gate transistors reveal the potential of this device architecture for practical memory applications. (C) 2013 AIP Publishing LLC.
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.
The formation mechanisms and optical characteristics of GaSb quantum rings
(2013-08-07)
Lin, Wei-Hsun
;
Wang, Kai-Wei
;
Liao, Yu-An
;
Pao, Chun-Wei
;
Lin, Shih-Yen
The growth mechanisms and optical characteristics of GaSb quantum rings (QRs) are investigated. Although As-for-Sb exchange is the mechanism responsible for the dot-to-ring transition, significant height difference between GaSb quantum dots (QDs) and QRs in a dot/ring mixture sample suggests that the dot-to-ring transition is not a spontaneous procedure. Instead, it is a rapid transition procedure as long as it initiates. A model is established to explain this phenomenon. Larger ring inner diameters and heights of the sample with longer post Sb soaking time suggest that As-for-Sb exchange takes places in both vertical and lateral directions. The decreasing ring densities, enlarged ring inner/outer diameters and eventually flat GaSb surfaces observed with increasing growth temperatures are resulted from enhanced adatom migration and As-for-Sb exchange with increasing growth temperatures. (C) 2013 AIP Publishing LLC.
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