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 tech niques, predominantly x-ray crystallography using diamond anvil cells, are covered first. The relative equilibrium stability of these phases, as deter mined by theoretical methods, is also discussed. Metastable phases and the processing techniques by which they can be made are examined, introducing t he importance of phase transition kinetics in determining what is actually seen. Elastic and vibrational properties are then considered, looking at how elas tic constants and phonon frequencies are affected by increasing pressure an d how this can help us to understand the phase diagram and transition kinet ics. Finally, using these ideas, it is shown how one can formulate equilibr ium 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 semicond uctors and their high-pressure phases.