Wannier Exciton in an Electric Field. I. Optical Absorption by Bound and Continuum States

A comprehensive study of electric field effects on optical absorption by Wannier excitons is presented, showing field effects on both bound and continuum states. The calculations and results have been simplified by defining appropriate dimensionless parameters such that the eigenvalues are independent of field when expressed in terms of these parameters. A general normalization procedure for wave functions with continuous eigenvalues is outlined. The effect of the electron-hole interaction on the electric-field-induced oscillations is demonstrated, with the result that the electron-hole interaction enhances these oscillations near an $M_0$-type edge (positive effective masses) and quenches these oscillations near an $M_3$-type edge (negative effective masses). This effect would inhibit the observation of $M_3$-type edges in electroreflectance.