PIEZO-OPTICAL RESPONSE OF GE IN THE VISIBLE UV RANGE

Using rotating-analyzer ellipsometry we have measured the three complex components P11(omega), P12(omega), and P44(omega) of the linear piezo-optical tensor P(ijkl)(omega) of Ge in the 1.6 - 5.6 eV photon energy range. This was accomplished by applying static uniaxial stress to Ge crystals along the [111) and [001] crystallographic directions, and monitoring the stress-induced changes in the dielectric function epsilon(omega) at room temperature. The real and imaginary parts of each component were directly obtained. They show, in genera.1, good Kramers-Kronig consistency. A comparison with pseudopotential calculations of P11(omega), P12(omega), and P44(omega) for strained Ge is also given. In addition, deformation-potential constants (D1(1), D1(5), D3(3), D3(5)) and spin-exchange parameters (delta(J1), delta(J2)) were determined for the E1 - E1 + DELTA-1 transitions; they show good agreement with prior work.