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A high sensitivity triple-coupled quantum well infrared photodetector (TC-QWIP) based on high strain InGaAs/AlGaAs/InGaAs material system has been demonstrated. It consists of a high strain Si-doped In0.25Ga0.75As quantum well and two undoped thin Al0.11Ga0.89As/In0.12Ga0.88As quantum wells (QWs) separated by a thick Al0.11Ga0.89As barrier layer. We also investigate the performance dependence of this QWIP with two different numbers of quantum well periods (5- and 10-period). Two response peaks at 9.5 micrometer and 7 micrometer were observed under different negative bias conditions, which are attributed to the transitions from the ground state to the second excited states and the continuum states, respectively. Spectral responsivities of 2.77 A/W and 1.55 A/W and the BLIP detectivities of 2.24 X 1010 cm-Hz1/2/W and 1.68 X 1010 cm-Hz1/2/W were obtained at Vb equals -3 V and (lambda) p equals 9.6 micrometer with 45 degree facet illumination and normal incidence illumination, respectively, for the 5-period device. As to the 10-period device, spectral responsivities of 2.7 A/W and 1.05 A/W and the BLIP detectivities of 2.21 X 1010 cm-Hz1/2/W and 1.38 X 1010 cm-Hz1/2/W were obtained at Vb equals -5 V and (lambda) p equals 9.6 micrometer with 45 degree facet illumination and normal incidence illumination, respectively, for this device. This represents the highest normal incidence response ever reported for a QWIP operating at 9.6 micrometer peak wavelength. Based on the responsivity and detectivity data the minimum detectable photon flux for this new device is found to be 1.08 X 1011 and 1.09 X 1011 cm-2s-1 for the 5-period and 10- period devices, respectively, at (lambda) p equals 9.6 micrometer, bandwidth equals 1 micrometer, and FOV equals 180 degrees. Thus, the HS-TC-QWIP reported here is capable for lower background IR imaging array applications.
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