Abstract
A tunable midinfrared photodetector using 1→4 intersubband Stark shift in the four-level AlInAs/GaInAs coupled quantum wells (CQWs) is proposed. The operation of this device is based on the infrared absorption by the electrons in the ground state transited from the ground-state subband E 1 of the CQWs to the third-excited-state subband E 4 . A large variation of eigenenergy spacing ΔE 41 between E 1 and E 4 under an applied electric field can be achieved for the proposed AlInAs/GaInAs CQW system. Since the infrared radiation is absorbed via the intersubband resonance absorption (h stroke signω=E 4 -E 1 ), the detected infrared wavelength can be tuned by the spacing ΔE 41 which can be adjusted by an applied electric field. The tunability of these AlInAs/GaInAs CQWs have been studied theoretically. Based on theoretical calculations, tuning ranges from 3 to 3.9 and 2.9 to 4.2 μm are predicted for the proposed asymmetric CQW structure and compositionally asymmetric CQW structure, respectively. This tuning capability is achieved by varying the applied electric field in the 90 to -90 kV/cm range.