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

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 (ΔE41). The amount of the Stark shift of calculated intersubband energy separation ΔE41 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 λ=3–5 μm 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 E1 transited to the third-excited-state subband E4 of the TCQW. Since the infrared radiation is absorbed via the intersubband resonance absorption (ℏω=E4−E1), the detected infrared wavelength can be tuned by the ΔE41 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 μm is predicted for the three-depth TCQW structure by varying the applied electric field in the 90 to −80 kV/cm range.