7 April 1999 Broadband quantum well infrared photodetectors
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Abstract
Typical quantum well infrared photodetectors (QWIPs) exhibit rather narrow spectral bandwidth of 1 to 2 micrometer. For certain applications, such as spectroscopy, sensing of a broader range of infrared radiation is highly desirable. In this work, we report the design of five broadband (BB-) QWIPs sensitive over the 7 to 14 micrometer spectral range. Three n- type BB-QWIPs consisting of three, four, and five quantum wells of different thickness and/or composition in a unit cell, which are then repeated 20 times for the three and four quantum wells (QW) devices and 3 times for the five QWs device to create the BB-QWIP structures, are demonstrated. The three- well n-type InxGa1-xAs/AlyGa1-yAs BB-QWIP is designed to have a response peak at 10 micrometer, with a FWHM bandwidth that varies with the applied bias. A maximum bandwidth of (Delta) (lambda) /(lambda) p equals 21% was obtained for this device at Vb equals -2 V. The four- well n-type InxGa1-xAs/GaAs BB-QWIP not only exhibits a very large responsivity of 2.31 A/W at 10.3 micrometer and Vb equals +4.5 V, but also achieves a broader bandwidth of (Delta) (lambda) /(lambda) p equals 29% than the three-well device. The five-well n-type InxGa1- xAs/GaAs BB-QWIP has achieved a FWHM bandwidth of (Delta) (lambda) /(lambda) p equals 28% at Vb equals 1.75 V. In addition, two p-type InxGa1-xAs/GaAs BB-QWIPs with variable well thickness and composition, sensitive in the 7 - 14 micrometer spectral range, are also demonstrated. The variable composition p-type BB-QWIP has a very large FWHM bandwidth of (Delta) (lambda) /(lambda) p equals 48% at Vb equals -1.5 V and T equals 40 K. The variable thickness p- type BB-QWIP was found to have an even broader FWHM bandwidth of (Delta) (lambda) /(lambda) p equals 63% at Vb equals 1.1 V and T equals 40 K, with a corresponding peak responsivity of 25 mA/W at 10.2 micrometer. The results reveal that p-type BB- QWIPs have a broader and flatter spectral bandwidth but lower responsivity than that of n-type BB-QWIPs under similar operating conditions.
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Sheng S. Li, Sheng S. Li, Jerome T. Chu, Jerome T. Chu, Jiangchi Chiang, Jiangchi Chiang, Jung Hee Lee, Jung Hee Lee, Anjali Singh, Anjali Singh, } "Broadband quantum well infrared photodetectors", Proc. SPIE 3629, Photodetectors: Materials and Devices IV, (7 April 1999); doi: 10.1117/12.344551; https://doi.org/10.1117/12.344551
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