Browsing by Author "Chao, Kuang-Ping"

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Broadband Quantum-Dot Infrared Photodetector
(2010-07-01)
Lin, Wei-Hsun
;
Tseng, Chi-Che
;
Chao, Kuang-Ping
;
Kung, Shu-Yen
;
Lin, Shih-Yen
In this letter, we report the five-period quantum-dot infrared photodetectors (QDIPs) with a bi-stacked quantum-dot (QD) structure for a wide and relatively flat detection response ranging from 4 to 11 m with high responsivities. The bi-stacked QD structure consists of a standard InAs QD and an InGaAs-capped InAs QD layer separated by a 50-nm GaAs barrier layer. The device exhibits a wide detection window in the range of 4-11 mu m with high responsivities, which suggests that similar responsivities can be obtained for the standard QD and the InGaAs-capped QD layers in the mid-wavelength (MWIR) and long-wavelength (LWIR) infrared ranges, respectively. The results are advantageous for the development of broadband QDIPs covering MWIR and LWIR ranges based on the stacked QD structures.
Enhancement of operation temperature of InAs/GaAs quantum-dot infrared photodetectors with hydrogen-plasma treatment
(2009-09-01)
Lin, Wei-Hsun
;
Tseng, Chi-Che
;
Chao, Kuang-Ping
;
Lin, Shih-Yen
;
Wu, Meng-Chyi
Postprocess hydrogen treatment is performed over fabricated ten-period InAs/GaAs quantum-dot infrared photodetectors. While keeping similar spectral responses at the same applied voltage, a reduced dark current is observed for the H-plasma-treated device, which is attributed to the suppression of surface leakage-current induced by surface damage during device processing. The significant reduction in dark current also enhanced the operation temperature of the device up to 100 K. Also observed are the smoothed-out mesa edges after the H-plasma treatment, which results in trapezoidal mesa edges. In this case, a longer propagation length in the device of the reflected incident light at the mesa edge would enhance the normal-incident absorption ratio of the H-plasma-treated device. (C) 2009 American Vacuum Society. [DOI:10.1116/1.3196781]
InGaAs-Capped InAs-GaAs Quantum-Dot Infrared Photodetectors Operating in the Long-Wavelength Infrared Range
(2009-09-15)
Lin, Wei-Hsun
;
Tseng, Chi-Che
;
Chao, Kuang-Ping
;
Mai, Shu-Cheng
;
Lin, Shih-Yen
A ten-period InAs-GaAs quantum-dot infrared photodetector (QDIP) with 8-nm In(0.15)Ga(0.85) As capping layer grown after quantum-dot (QD) deposition is investigated. With reduced InAs QD coverage down to 2.0 mono-layers, responses at 10.4 and 8.4 mu m are observed for the device under positive and negative biases, respectively. The phenomenon is attributed to the large Stark effect resulted from the asymmetric band diagrams of the device under different voltage polarities. The demonstration of long-wavelength infrared detections with the simple structures of the InGaAs-capped QDIP is advantageous for the development of multicolor QDIP focal-plane arrays.
The influence of In composition on InGaAs-capped InAs/GaAs quantum-dot infrared photodetectors
(2009-09-01)
Lin, Wei-Hsun
;
Chao, Kuang-Ping
;
Tseng, Chi-Che
;
Mai, Shu-Cheng
;
Lin, Shih-Yen
The influence of an additional InGaAs-capped layer on the performance of InAs/GaAs quantum-dot infrared photodetectors (QDIPs) is investigated. For the device with a 15% InGaAs-capped layer, a significant response at 7.9 mu m is observed for the QDIP device. The results suggest that with the additional InGaAs-capped layer, the detection wavelengths of the InAs/GaAs QDIPs could be shifted to a longer-wavelength infrared range. A further increase in the In composition will not help to obtain an even longer-wavelength detection, which is attributed to the cancellation of a lower InGaAs state, and InAs-QD bandgap shrinkage resulted from the relaxed compressive strains of the InGaAs layer with a higher In composition.
Transition mechanism of InAs/GaAs quantum-dot infrared photodetectors with different InAs coverages
(2010-05-01)
Tseng, Chi-Che
;
Chung, Tung-Hsun
;
Mai, Shu-Cheng
;
Chao, Kuang-Ping
;
Lin, Wei-Hsun
In this article, the authors investigate the influences of different InAs coverages on the photoluminescence excitation (PLE) spectra and spectral responses of InAs/GaAs quantum-dot infrared photodetectors (QDIPs). An increase in InAs coverage would lead to an increase in energy separation between heavy-hole state and light-hole state in the wetting layer (WL) region in the QD PLE spectra. The results suggest that most of the strain resulted from the InAs/GaAs lattice mismatch may be accumulated in the WL instead of the QD region. Also observed are the similar energy separations of energy levels responsible for the intraband absorption in the PLE spectra of the QDIPs such that similar detection wavelengths are observed for the devices. [DOI:10.1116/1.3368607]
Voltage-tunable two-color quantum-dot infrared photodetectors
(2009-09-21)
Lin, Shih-Yen
;
Lin, Wei-Hsun
;
Tseng, Chi-Che
;
Chao, Kuang-Ping
;
Mai, Shu-Cheng
A two-terminal quantum-dot infrared photodetector with stacked five-period InAs/GaAs and InGaAs-capped InAs/GaAs quantum-dot (QD) structures is investigated. The device has exhibited distinct responses at mid-wavelength and long-wavelength infrared regions under positive and negative biases, respectively. The results suggest that the QD confinement states near the anode side are completely filled, such that selective responses at different wavelength ranges would be observed for the stacked structure under different voltage polarities. Also observed are the similar absorption ratios of the device under different incident light polarizations at the two response regions. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3236543]
Wavelength-Tunable InGaAs-Capped Quantum-Dot Infrared Photodetectors
(2010-02-15)
Lin, Wei-Hsun
;
Tseng, Chi-Che
;
Chao, Kuang-Ping
;
Mai, Shu-Cheng
;
Lin, Shih-Yen
Quantum-dot infrared photodetectors (QDIPs) with InGaAs capping layers are investigated. Compared with the standard QDIP with 2.5-mono-layer (ML) InAs QDs, the detection wavelength is shifted from 6 to 7.9 m for an 8-nm InGaAs-capped QDIP. By decreasing the QD coverage from 2.5 to 2.0 ML, an even longer detection wavelength 10.4 m is observed, which is attributed to the higher energy levels of the QD excited states resulted from the smaller QDs. By further increasing the capping layer thickness to 12 nm, longer detection wavelengths with broad response 10-18 m is observed for the InGaAs-capped QDIP.
Wavelength-tunable InGaAs-capped quantum-dot infrared photodetectors for multi-color detection
(2011-05-01)
Lin, Wei-Hsun
;
Lin, Shih-Yen
;
Tseng, Chi-Che
;
Kung, Shu-Yen
;
Chao, Kuang-Ping
A two-terminal quantum-dot infrared photodetector (QDIP) with stacked 5-period InAs/GaAs and InGaAs-capped InAs/GaAs QD structures is investigated in this paper. The device has exhibited distinct responses at mid-wavelength and long-wavelength infrared regions under positive and negative biases, respectively. Also observed for the device are the equal normal absorption ratios under different voltage biases for the device under either MWIR or LWIR ranges. The device has revealed its potential in the application of voltage-tunable and multi-color detections. (C) 2010 Elsevier B.V. All rights reserved.