Screened excitons in wide-gap semiconductors and quantum wells

The variable-phase approach is applied to scattering and bound states in screened Coulomb potentials in two and three dimensions. The degree of ionisation for the electron-hole plasma is calculated taking into account scattering in the continuum. A two-dimensional formulation of Levinson's theorem is used for bound-state counting and a simple relationship between the screening length and the number of bound states is found for an attractive Coulomb potential screened by a two-dimensional electron gas. © 1998 Elsevier Science B.V. All rights reserved.