High-pressure phases of group IV and III-V semiconductors

The currently known structures and properties of group IV elements and III-V compounds at high pressure are reviewed. Structural properties of various phases, as determined by experimental techniques, predominantly x-ray crystallography using diamond anvil cells, are covered first. The relative equilibrium stability of these phases, as determined by theoretical methods, is also discussed. Metastable phases and the processing techniques by which they can be made are examined, introducing the importance of phase transition kinetics in determining what is actually seen. Elastic and vibrational properties are then considered, looking at how elastic constants and phonon frequencies are affected by increasing pressure and how this can help us to understand the phase diagram and transition kinetics. Finally, using these ideas, it is shown how one can formulate equilibrium pressure-temperature equations of state for these materials. Throughout, the review draws on both experimental and theoretical work, and emphasizes features which seem to be generic to these tetrahedral semiconductors and their high-pressure phases.