STRONG STARK-EFFECT OF THE INTERSUBBAND TRANSITIONS IN THE 3 COUPLED QUANTUM-WELLS - APPLICATION TO VOLTAGE-TUNABLE MIDINFRARED PHOTODETECTORS

The quantum-confined Stark effect in the AlInAs/GaInAs three-coupled-q uantum-well (TCQW) structures is studied theoretically. The basic AlIn As/GaInAs TCQW structures are composed of three GaInAs quantum wells s eparated by two narrow AlInAs barriers. Results indicated that the thr ee-depth TCQW structure exhibits a very large and near-linear voltage- control Stark shift for the energy of the 1-->4 intersubband transitio n (Delta E(41)). The amount of the Stark shift of calculated intersubb and energy separation Delta E(41) is about 175 meV as the applied elec tric 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 t he enhanced Stark shift of the 1-->4 intersubband transition in the th ree-depth TCQW structure, a highly sensitive voltage-tunable midinfrar ed 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 abso rption (($) over bar h omega=E(4)-E(1)), the detected infrared wavelen gth can be tuned by the Delta E(41) which can be adjusted by an applie d electric field. The tunability of this three-depth TCQW structure ha s been studied theoretically. Based on the theoretical calculations, a tuning range from 3 to 5 mu m is predicted for the three-depth TCQW s tructure by varying the applied electric field in the 90 to -80 kV/cm range. (C) 1995 American Institute of Physics.