Browsing by Author "Hsu, Wei-Cheng"

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Characteristics of surface plasmon coupled quantum well infrared photodetectors
(2017-06-28)
Hsu, Wei-Cheng
;
Ling, Hong-Shi
;
Wang, Shiang-Yu
;
Lee, Chien-Ping
;
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
;
Ling, Hong-Shi
;
Wang, Shiang-Yu
;
Lee, Chien-Ping
;
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.
Voltage-tunable dual-band quantum dot infrared photodetectors for temperature sensing
(2012-05-07)
Ling, Hong-Shi
;
Wang, Shiang-Yu
;
Hsu, Wei-Cheng
;
Lee, Chien-Ping
;
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
;
Ling, Hong-Shi
;
Wang, Shiang-Yu
;
Lee, Chien-Ping
;
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