Phase transitions in 2D semiconductor systems

The high-pressure phase transitions and the thermodynamic stability of single and repeated semiconductor heterostructures are influenced by interface epitaxy as well as bulk properties. High-pressure optical microscopy and Raman experiments on AlAs/GaAs superlattices have demonstrated several novel phase transition phenomena, which are discussed. A theory is presented that explains these phenomena, and other consequences of interface-altered stability, in terms of the energy competition between misfit dislocations and interface strain. 'Phase diagrams' plotting transition pressure versus superlattice layer width are calculated and found to compare favourably with experiment.