A voltage-tunable multicolor triple-coupled InGaAs/GaAs/AlGaAs quantum-well infrared photodetector for 8–12 μm detection

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Abstract
A voltage‐tunable multicolor triple‐coupled quantum‐well infrared photodetector (TC‐QWIP) has been developed for 8–12 μm detection. The TC‐QWIP consists of three coupled quantum wells formed by an enlarged Si‐doped InxGa1−xAs quantum well and two undoped GaAs quantum wells separated by two thin AlyGa1−yAs barriers. Two TC‐QWIP structures with varying indium and aluminum compositions were designed and demonstrated. Due to the strong coupling effect of the asymmetrical quantum wells, three bound states (E1, E2, E3) are formed inside the quantum wells of the TC‐QWIP. The main detection peak wavelength is due to E1→E3 bound states transition for both devices, while two secondary detection peaks due to E1→E2 and E1→Ec continuum states transitions under different biases were also observed. In addition, a strong quantum‐confined Stark shift effect for the E1→E3 transition was observed in the wavelength range of 8.2–9.1 and 10.8–11.5 μm for QWIP‐A and QWIP‐B, respectively; both devices exhibit a linear dependence of detection peak wavelength on the applied bias voltage. A spectral responsivity of Ri=0.05 A/W and background limited performance (BLIP) detectivity DBLIP*=6.1×109 cm√Hz/W were obtained at Vb=5 V, λp=8.6 μm, and TBLIP=66 K for QWIP‐A, while Ri=0.33 A/W and DBLIP* =1.63×1010 cm√Hz/W at Vb=4 V, λp=11.2 μm, and TBLIP=50 K were obtained for QWIP‐B.

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