Low dark current dual band infrared photodetector using thin AlAs barriers and Γ-X mixed intersubband transition in GaAs quantum wells

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Abstract
A low dark current dual band quantum well infrared photodetector is demonstrated by adding thin AlAs barriers to the usual detector structure, which consists of Si‐doped GaAs wells separated by thick AlGaAs barriers. The advantages of adding the thin AlAs barriers to clad the quantum wells are that (a) the detector displays a low dark current and (b) intersubband photocurrents result from transitions from both the Γ ground to the first excited state, and from the Γ ground to a mixed Γ‐X excited state because the X‐valley band edge forms a well in AlAs and intrinsic Γ‐X mixing occurs. The spectral peaks of these two transitions, which occur at 8.5 and 5.5 μm in our test structure, can be varied by changing device parameters during growth.