ENHANCEMENT OF THE STARK-EFFECT IN ALINAS/GAINAS COUPLED QUANTUM-WELLS AND THEIR APPLICATIONS TO TUNABLE MIDINFRARED PHOTODETECTORS

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 E1 of the CQWs to the third-excited-state subband E4. A large variation of eigenenergy spacing DELTAE41 between E1 and E4 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 (homegaBAR = E4-E1), the detected infrared wavelength can be tuned by the spacing DELTAE41 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 mum are predicted for the proposed asymmetric CQW structure and compositionally asymmetric COW structure, respectively. This tuning capability is achieved by varying the applied electric field in the 90 to -90 kV/cm range.