A THEORETICAL INVESTIGATION ON THE QUANTUM-FIELD EFFECT DIRECTIONAL COUPLER

A theoretical investigation on the quantum field effect directional co upler is presented. The behavior of electrons in the device is studied by solving the Schrodinger equation directly. The complete transfer e ffect is revealed to be an intrinsic property of the parity symmetry o f the system. Transfer length is precisely calculated by using the tra nsfer matrix method. Two model transverse confinements have been used in the calculation. One is a symmetric double rectangular well; and th e other is a symmetric double finite-parabolic potential. Conductance of the device is investigated by applying the Landauer formula. Conduc tance oscillations with Fermi energy and barrier height are obtained. One method of determining the transfer length from the curve of conduc tance vs barrier height is proposed. Special attention is paid to the multimodedness of the device. Correlation among the different modes is demonstrated to reduce the transfer effect of the device. Reflection at the interfaces between uncoupled and coupled waveguides is proved t o be negligible.