Effect of anisotropic strain on the crosshatch electrical activity in relaxed GeSi films

The physical origin of the crosshatch electrical activity in relaxed GeSi films was studied using a near-field scanning optical microscope (NSOM). The contrast and patterns in the near-field photocurrent images depend on the polarization direction of the NSOM light. These results rule out composition nonuniformity, junction depth variation, and scanning artifacts as dominant sources of the contrast. Numerical calculations show that local changes in band structure due to strain fields of the misfit dislocations are responsible for the experimental observations.