PIEZOOPTICAL RESPONSE OF SEMICONDUCTORS

The effects of uniaxial stress on the optical properties of Si, Ge, GaAs, InP and GaP have been investigated using rotating analyser ellipsometry. Under the presence of an external stress described by the second-rank tensor X(ij), changes in the dielectric tensor epsilon(ij)(omega) are linked to X(ij) by the fourth-rank symmetric tensor (piezo-optical tensor) P(ijkl)(omega) such that DELTAepsilon(ij)(omega) = P(ijkl)(omega)X(ij). For diamond and zinc blende types of semiconductors three independent functions P11(omega), P12(omega) and P44(omega) are required to characterize this tensor fully. Measurements of these functions were performed at room temperature, with the optical path kept in air, in the visible range (homegaBAR almost-equal-to 1. 5 - 5.4 eV) and the values compared with extensive existing information (polarized reflectivity and piezoreflectance) as well as calculations with the empirical pseudopotential method. We review the piezoellipsometry technique and present some new results.