Abstract
We report four different InGaAs/AlGaAs multi-color, broadband (BB) quantum well infrared photodetectors (QWIPs) with digital graded superlattice barrier (DGSLB) and linear-graded barrier (LGB) for long wavelength infrared (LWIR) detection. The two DGSLB-QWIPs were grown using compositionally DGSLB structures with GaAs/Al 0.15Ga 0.85As material system to create a staircase-like band gap variation in the barrier region. A BB spectral response (7–16 μm) was obtained under positive biases while a normal spectral response ( λ p=11 μm) was obtained under negative biases in the BB-DGSLB-QWIP. A high sensitivity double barrier (DB)-DGSLB-QWIP with a thin undoped Al 0.15Ga 0.85As DB grown on both side of the quantum well has also been studied. A normal spectral response with peak wavelength at 12 μm was obtained in this device under both positive and negative biases. In addition, two InGaAs/AlGaAs QWIPs using Al x Ga 1– x As LGB with and without AlGaAs DB layers have also been investigated. For the BB-LGB-QWIP, the BB spectral response was obtained under positive biases while the voltage-tunable multi-color detection with two peaks were obtained at negative biases. A very high responsivity was achieved in the DB-LGB-QWIP.
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