EFFECT OF PRESSURE ON THE REFRACTIVE-INDEX OF GE AND GAAS

We have measured the dispersion of the refractive index n() of Ge and GaAs between 0.6 and 1.4 eV for hydrostatic pressures up to 8 GPa. The frequency dependence of n() is extrapolated to zero energy by using an oscillator model of the dielectric function. In this way, we obtain the variation with pressure of the electronic static dielectric constant . We find that for the volume change of V/V08% covered in this experiment the volume dependence of is well described by a single scaling coefficient r=d ln/d lnV with r=1.58(3) for Ge and 0.73(4) for GaAs. Results are discussed in relation to semiempirical theoretical models. © 1990 The American Physical Society.