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

TL;DR

This paper calculates the ionization degree of electron-hole plasma in semiconductor quantum wells, revealing significant deviations from classical models and differences between semiconductor types at room temperature.

Contribution

It introduces a modified law of mass action incorporating all bound and unbound states using the variable phase method for better plasma ionization modeling.

Findings

Strong deviation from standard law of mass action due to scattering states

Qualitative differences between mid- and wide-gap semiconductors

At room temperature, wide-gap semiconductors have a balanced mixture of correlated pairs and free carriers

Abstract

The degree of ionization of a nondegenerate two-dimensional electron-hole plasma is calculated using the modified law of mass action, which takes into account all bound and unbound states in a screened Coulomb potential. Application of the variable phase method to this potential allows us to treat scattering 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 mid- and wide-gap semiconductors is demonstrated. For wide-gap semiconductors at room temperature, when the bare exciton binding energy is of the order of T, the equilibrium consists of an almost equal mixture of correlated electron-hole pairs and uncorrelated free carriers.