The Metal‐Insulator Transition in Electron‐Hole Systems

Theoretical studies of the metal‐insulator transition in electron‐hole systems in indirect semiconductors are presented. The model is based on various screening theories and on thermodynamical continuity requirements. In case of Debye‐Hückel‐like screening the phase diagrams of Si and Ge contain two separate transitions, the gas‐liquid and the metal‐insulator transition. Stronger and weaker dependence of the band energies on the free pair density favors the metal‐insulator and the gas‐liquid transition, respectively.