D-CENTERS IN SPHERICAL QUANTUM DOTS

A negatively charged donor center D- (i.e., a neutral shallow donor D0 that binds a second electron) in a spherical quantum dot is studied by use of a variational approach. A trial function which includes electron-correlation effects and approaches the Chandrasekhar-type function in the limit of zero barrier height is used. The well-radius and barrier-height dependence of the "binding energy" of the D- center is obtained. The dimensional characteristics are clearly demonstrated not only for the "binding energy" and its maximum of the D- center but also for the ratio of D- to D0 "binding energy" and the electron-correlation effect.