Browsing by Author "Ling, Hong-Shi"

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Characteristics of surface plasmon coupled quantum well infrared photodetectors
(2017-06-28)
Hsu, Wei-Cheng
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Ling, Hong-Shi
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Wang, Shiang-Yu
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Lee, Chien-Ping
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電機學院
Quantum Well Infrared Photodetectors (QWIPs) with different structures were characterized for the study of surface plasmon wave coupling. Detailed comparisons between surface plasmon coupled and etched grating coupled devices were investigated. A bias dependence for the enhancement of the responsivity of surface plasmon coupled devices was found, especially for the samples with non-uniform quantum wells. The non-uniform QWIPs with surface plasmon coupling showed an asymmetric enhancement with respect to the bias directions. Stronger enhancements were shown under the biases when a higher effective electric field region is close to the collector. The change of the photocarrier escape probability due to the narrow coupling bandwidth of the surface plasmon wave is attributed to this unexpected bias dependence. Published by AIP Publishing.
Dependence of Performance of Surface Plasmon Coupled Quantum Well Infrared Photodetectors on Doping
(2018-11-01)
Hsu, Wei-Cheng
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Ling, Hong-Shi
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Wang, Shiang-Yu
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Lee, Chien-Ping
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電子工程學系及電子研究所
Three samples of Quantum Well Infrared Photodetectors (QWIPs) with different well doping were proposed for comparison between metallic grating and etched grating. All different doping samples with detectivity 1x10(11) cm*Hz(0.5)/W were achieved under 77 K with metallic grating and the highest detectivity was 2.92x10(11) cm*Hz(0.5)/W with 3.3E17 cm(-3) well doping. The metallic grating samples showed a different quantum efficiency (QE) increment behavior from the etched grating samples as we increased the well doping. The QE enhancement of metallic grating sample was smaller than that in positive bias due to the potential spike between the AlGaAs/GaAs interface. The metallic grating device is more sensitive to the extra barrier between the AlGaAs/GaAs interface because of a narrower coupling bandwidth of surface plasmon. Though the enhancement varied between different samples as we changed the well dopings, the detectivity could still be kept within a reasonable range, which is important for focal plane array applications.
Evolution of self-assembled InAs quantum ring formation
(2007-07-15)
Ling, Hong-Shi
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Lee, Chien-Ping
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
The evolution of InAs quantum ring (QR) formation and the corresponding optical properties were investigated by atomic force microscopy (AFM) and photoluminescence (PL) spectroscopy. Just like a nanoscale volcanic eruption, the transformation from quantum dots (QDs) to QRs using the capping and annealing process depends on how much InAs is removed from the center of the dots to the surrounding areas. The final structure was found to depend on the annealing temperature and the cap layer thickness. We have investigated the QR formation at different stages using various growth conditions. The findings provided a clear picture on the mechanism of ring formation. We were able to obtain QRs with various geometries by controlling these growth parameters. (c) 2007 American Institute of Physics.
Impacts of structural asymmetry on the magnetic response of excitons and biexcitons in single self-assembled In(Ga)As quantum rings
(2009-08-01)
Lin, Ta-Chun
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Lin, Chia-Hsien
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Ling, Hong-Shi
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Fu, Ying-Jhe
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Chang, Wen-Hao
The diamagnetic shifts of neutral excitons and biexcitons confined in single self-assembled In(Ga)As/GaAs quantum rings are investigated. Unlike quantum dots, quantum rings reveal a considerably large biexciton diamagnetic shift, about two times larger than that of single excitons. Based on model calculations, we found that the inherent structural asymmetry and imperfection, combined with the interparticle Coulomb interactions, is the fundamental cause of the more extended biexciton wave function in the quantum rings. The exciton wave function tends to be localized in one of the potential valleys induced by structural imperfections of the quantum ring due to the strong localization of hole and the electron-hole Coulomb attraction, resembling the behavior in single dots. Our results suggest that the phase coherence of neutral excitons in quantum rings will be smeared out by such wave function localizations.
Long-Wavelength Quantum-Dot Infrared Photodetectors With Operating Temperature Over 200 K
(2009-01-01)
Ling, Hong-Shi
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Wang, Shiang-Yu
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Lee, Chien-Ping
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Lo, Ming-Cheng
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電子工程學系及電子研究所
We demonstrate the high-temperature operation of confinement enhanced dots-in-a-well (CE-DWELL) quantum-dot infrared photodetectors (QDIPs). The thin Al(0.3)Ga(0.7)As barrier layer added above the InAs QDs greatly improve the lateral confinement of QD states in the In(0.15)Ga(0.85)M DWELL structure and the device performance. With better device parameters of CE-DWELL, it is possible to achieve high quantum efficiency, high operating temperature, and long-wavelength detection at the same time.
Vertically Coupled Quantum-Dot Infrared Photodetectors
(2010-06-01)
Lo, Ming-Cheng
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Wang, Shiang-Yu
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Ling, Hong-Shi
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Lee, Chien-Ping
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電子工程學系及電子研究所
Vertically coupled InAs-GaAs quantum-dot infrared photodetectors (QDIPs) were studied in this letter. With vertically coupled quantum dots (QDs), the QDs in the same column share the same electronic states which remove the QD size variation effect in the growth direction and result in a narrow response band and higher peak quantum efficiency. The coupled states increase the capture probability and also facilitate the carrier flow among QD layers. The frequency response of vertically coupled QDIPs is much faster than that of the conventional ones.
Voltage-tunable dual-band quantum dot infrared photodetectors for temperature sensing
(2012-05-07)
Ling, Hong-Shi
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Wang, Shiang-Yu
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Hsu, Wei-Cheng
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Lee, Chien-Ping
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電子工程學系及電子研究所
We report voltage-tunable 3-5 mu m & 8-12 mu m dual-band detection in the InAs/Al0.3Ga0.7As/In0.15Ga0.85As confinement-enhanced dots-in-a-well quantum dot infrared photodetectors. The capability in temperature sensing is also demonstrated. Distinct response peaks at 5.0 mu m and 8.6 mu m were observed in the photocurrent spectra with working temperature up to 140K. The two peaks correspond to the transition paths from the quantum dot ground state to the quantum well state and the quantum dot excited state, respectively. At 77K, the response ratio of the 8.6 mu m peak over the 5.0 mu m peak changes from 0.29 at -3V to 5.8 at + 4.8V. Excellent selectivity between the two peaks with bias voltage makes the device attractive for third-generation imaging systems with pixel-level multicolor functionality. (C)2012 Optical Society of America
Wavelength tuning of surface plasmon coupled quantum well infrared photodetectors
(2018-01-08)
Hsu, Wei-Cheng
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Ling, Hong-Shi
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Wang, Shiang-Yu
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Lee, Chien-Ping
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電機學院
A novel method of detection wavelength tuning for surface plasmon coupled quantum well infrared photodetectors (QWIPs) was demonstrated. By changing of the thickness of the top contact layer, the detection wavelength can be adjusted. The displacement of the detection wavelength is related to the effective dielectric constant of the dielectric layers in the device structure. The peak wavelength moves toward longer wavelength as the contact layer thickness decreases. With a proper match of the 2D metal hole array and the QW absorption region, the responsivity can be kept within a reasonable range for samples with different top contact layer thicknesses. (c) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement