ELECTRIC-FIELD-DEPENDENT ABSORPTION OF ZNSE-BASED QUANTUM-WELLS - THETRANSITION FROM 2-DIMENSIONAL TO 3-DIMENSIONAL BEHAVIOR

The absorption coefficient of ZnxCd1-xSe/ZnSySe1-y quantum-well struct ures in a strong electric field is investigated as it depends on the q uantum-well width. A quantum-mechanical model is developed which fully takes account of the Coulomb interaction leading to intersubband coup ling and strong excitonic effects. Numerical results are presented and compared with measurements. The study focuses on the transition regim e between the quantum-confined Stark effect, which is found for well w idths smaller than the exciton Bohr diameter, and the Franz-Keldysh ef fect, which corresponds to the limit of wide wells. Our theory allows for a unified treatment of a wide range of quantum-well widths and app lied fields, and provides detailed insight into the origin of the stru cture of the absorption spectrum through a spatially resolved microsco pic absorption coefficient. [S0163-1829(98)01840-2].