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Investigation of broad-band quantum-well infrared photodetectors for 8-14-μm detection

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3 Author(s)
Chu, J. ; Dept. of Electr. & Comput. Eng., Florida Univ., Gainesville, FL, USA ; Li, Sheng S. ; Singh, A.

Typical quantum-well infrared photodetectors (QWIPs) exhibit a rather narrow spectral bandwidth of 1-2 μm. For certain applications, such as spectroscopy, sensing a broader range of infrared radiation is highly desirable. In this paper, we report the design of four broad-band QWIPs (BB-QWIPs) sensitive over the 8-14-μm spectral range. Two n-type BB-QWIPs, consisting of three and four quantum wells of different thickness and/or composition in a unit cell which is then repeated 20 times to create the BB-QWIP structure, are demonstrated. The three-well n-type InxGa1-xAs-AlyGa1-yAs BB-QWIP was designed to have a response peak at 10 μm, with a full-width at half-maximum (FWHM) bandwidth that varies with the applied bias. A maximum bandwidth of Δλ/λp=21% was obtained for this device at Vb=-2 V. The four-well n-type InxGa1-xAs-GaAs BB-QWIP not only exhibits a large responsivity of 2.31 A/W at 10.3 μm and Vb=+4.5 V, but also achieves a bandwidth of Δλ/λp=29% that is broader than the three-well device. In addition, two p-type In xGa1-xAs-GaAs BB-QWIPs with variable well thickness and composition, sensitive in the 7-14-μm spectral range, are also demonstrated. The variable composition p-type BB-QWIP has a large FWHM bandwidth of Δλ/λp=48% at T=40 K and Vb=-1.5 V. The variable thickness p-type BB-QWIP was found to have an even broader FWHM bandwidth of Δλ/λ p=63% at T=40 K and Vb=1.1 V, with a corresponding peak responsivity of 25 mA/W at 10.2 μm. The results show that a broader and flatter spectral bandwidth was obtained in both p-type BB-QWIP's than in the n-type BS-QWIP's under similar operating conditions

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Quantum Electronics, IEEE Journal of  (Volume:35 ,  Issue: 3 )