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7 April 1999 Broadband quantum well infrared photodetectors
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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.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Sheng S. Li, Jerome T. Chu, Jiangchi Chiang, Jung Hee Lee, and Anjali Singh "Broadband quantum well infrared photodetectors", Proc. SPIE 3629, Photodetectors: Materials and Devices IV, (7 April 1999);

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