Ionization degree of the electron-hole plasma in semiconductor quantum wells

The degree of ionization of a nondegenerate two-dimensional electron-hole p lasma is calculated using the modified law of mass action, which takes into account all bound and unbound states in a screened Coulomb potential. Appl ication of the variable phase method to this potential allows us to treat s cattering and bound states on the same footing. Inclusion of the scattering states leads to a strong deviation from the standard law of mass action. A qualitative difference between midgap and wide-gap semiconductors is demon strated. For wide-gap semiconductors at room temperature, when the bare exc iton binding energy is of the order of k(B)T, the equilibrium consists of a n almost equal mixture of correlated electron-hole pairs and uncorrelated f ree carriers. [S0163-1829(99)03532-8].