FREE AND ACCEPTOR-BOUND EXCITONS IN THE TRANSITION REGION BETWEEN 2-DIMENSIONAL AND QUASI-3-DIMENSIONAL GAAS ALXGA1-XAS SYSTEMS

The transition from a two-dimensional to a quasi-three-dimensional ele ctron system has been studied in multiple quantum wells, by varying th e barrier thickness L(b) for a constant 100-angstrom well width. Drama tic differences in electron-hole correlation are observed due to the d ifferent extension of electron and hole wave functions. The 1S-2S ener gy separation of the heavy-hole exciton decreases from 8.3 meV for L(b ) = 150 angstrom to 3.1 meV for L(b) = 10 angstrom. The acceptor-bound -exciton binding energy is constant, while the bound-exciton decay tim e increases dramatically with decreasing L(b).