Very large Stark shift in three-coupled-quantum wells and their application to tunable far-infrared photodetectors

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Abstract
[[abstract]]The quantum-confined Stark effect in the three-coupled-quantum-well (TCQW) structure is studied theoretically in this paper. The basic TCQW structures are composed of three quantum wells separated by two thin barriers. Coupled one-dimensional Schroedinger and Poisson equations are solved self-consistently to find the sub-band eigenenergies and the envelope wave functions for the TCQW structures. Results indicate that the GaInAs/AlGaAs/GaAs two-depth TCQW structure exhibits both a very large Stark shift and a high absorption coefficient for the 1→3 intersub-band transition. By using a 1→3 intersub-band Stark shift in the two-depth TCQW structure, a highly sensitive tunable far-infrared photodetector is proposed. This photodetector is ideal for device applications in the 8-14 μm atmospheric window region. The operation of this device is based on the infrared absorption by electrons in the ground state transited from the ground-state sub-band E1 of the TCQW to the second-excited-state sub-band E3. A very large variation of eigenenergy spacing ΔE31 between E3 and E1 under an applied electric field can be achieved. Since the infrared radiation is absorbed via the intersub-band resonance absorption (ℏω=E3-E1), the detected infrared wavelength can be tuned by the ΔE31 which can be adjusted by an applied electric field. Based on the theoretical calculations, a tuning range from 7.4 to 14 μm is predicted for the two-depth TCQW structure. This tuning capability is achieved by varying the applied electric field in the 60 to -60 kV/cm range[[fileno]]2030103010012[[department]]電機工程學