PIEZOOPTICAL PROPERTIES OF SI

The deformation potentials and the piezooptical properties of Si, for strain along the [001] and [111] directions, are investigated with the use of a realistic empirical tight-binding model. The values, as well as their sign, of the deformation potential constants D-1(1), D-1(5), D-3(3), and D-3(5) for the variation of the critical energy E-1 are e valuated for uniaxial and biaxial strain. The sign is found to be nega tive for D-1(1), D-3(3) and D-3(5) and positive for D-1(5). The dielec tric function of Si under pressure, as well as the reflectivity and th e linear piezooptical tenser components P-11(omega), P-12(omega) and P -44(omega) are also evaluated. The main structures in P-ij are located around the critical points E-1 and E-2.