Strong Stark effect of the intersubband transitions in the three coupled quantum wells: Application to voltage-tunable midinfrared photodetectors

摘要

[[abstract]]The quantum-confined Stark effect in the AlInAs/GaInAs three-coupled-quantum-well (TCQW) structures is studied theoretically. The basic AlInAs/GaInAs TCQW structures are composed of three GaInAs quantum wells separated by two narrow AlInAs barriers. Results indicated that the three-depth TCQW structure exhibits a very large and near-linear voltage-control Stark shift for the energy of the 1-->4 intersubband transition (Delta E(41)). The amount of the Stark shift of calculated intersubband energy separation Delta E(41) is about 175 meV as the applied electric field varied from -90 to 90 kV/cm. This large Stark shift can be exploited for fabricating a voltage-tunable midinfrared photodetector operating in lambda=3-5 mu m atmospheric window region. By employing the enhanced Stark shift of the 1-->4 intersubband transition in the three-depth TCQW structure, a highly sensitive voltage-tunable midinfrared photodetector is proposed. The operation of this device is based on the infrared absorption by electrons in the ground-state subband E(1) transited to the third-excited-state subband E(4) of the TCQW. Since the infrared radiation is absorbed via the intersubband resonance absorption (($) over bar h omega=E(4)-E(1)), the detected infrared wavelength can be tuned by the Delta E(41) which can be adjusted by an applied electric field. The tunability of this three-depth TCQW structure has been studied theoretically. Based on the theoretical calculations, a tuning range from 3 to 5 mu m is predicted for the three-depth TCQW structure by varying the applied electric field in the 90 to -80 kV/cm range.