IMPROVED MODELING OF EXCITONS IN TYPE-II SEMICONDUCTOR HETEROSTRUCTURES BY USE OF A 3-DIMENSIONAL VARIATIONAL FUNCTION

Binding energies and oscillator strengths of excitons in staggered-lin eup heterostructures such as type-II quantum wells are calculated by a variational method, using a single parameter. This method involves th e effective attractive potential imposed by the confined carrier to it s unconfined companion. Contrary to previous comparable works, a three -dimensional trial function of the variable r (r=\r(e)-r(h)\) is used, instead of a two-dimensional function of the in-plane projection rho. Due to the large spatial extension along z of the wave function of th e unconfined carrier, the latter approximation commonly used up to dat e, is too drastic, even though it works reasonably well for type-I sys tems. This is demonstrated by comparison of both hypotheses for GaAs-A lAs systems: when using the 3D function, binding energies are increase d by up to 52%, while electron-hole overlap integrals can be enhanced by one order of magnitude.