DEFECT-ENHANCED 2ND-HARMONIC GENERATION IN (SIMGEN)(P) SUPERLATTICES

Second-harmonic generation (SHG) has been applied to study the influen ce of defects in short-period (SimGen)(p) strained-layer superlattices . With a misfit stacking fault defect density of similar to 10(10) cm( -2) shown by transmission electron microscopy, it is found that the SH intensity increases by about one order of magnitude from that of the defect-for samples. We propose that the inhomogeneous strain field aro und the fault planes in the superlattice layers is responsible for thi s abrupt increase of SHG. The expected symmetry and the magnitude of t he nonlinear susceptibility from these stacking fault defects are show n to be in agreement with the experimental observations. (C) 1998 Amer ican Institute of Physics.