THERMAL-EXPANSION AND LATTICE-PARAMETERS OF GROUP-IV SEMICONDUCTORS

Thermal expansion is practically and theoretically important for predi cting residual stresses in epitaxial films and electronic devices as w ell as for providing information about the anharmonic properties of ma terials, and determining their equations of state. Model calculations have had difficulty in accurately representing thermal expansion at hi gh temperatures where such considerations are most important. We utili ze a semi-empirical quasi-harmonic model to evaluate available data fo r silicon and germanium. The model allows us to predict the thermal pr operties of these semiconductors from near 0 K to the vicinity of thei r melting points. The approach, consisting of a simplified frequency s pectrum with several Einstein terms, provides a convenient mathematica l method where a minimum of empirical parameters represent the thermal property.