2ND-HARMONIC GENERATION FROM CUINSE2 THIN-FILMS - INFLUENCE OF THE SUBSTRATE-EPILAYER LATTICE MISMATCH

We investigate the second-order nonlinear optical (NLO) properties of tetragonal chalcopyrite-structure CuInSe2 thin films using optical sec ond-harmonic generation at a fundamental wavelength of 790 nm. An appr oximate doubling of the second-order optical nonlinearity of the CuInS e2 thin films is achieved through changing the substrate from GaAs(001 ) to In0.29Ga0.71As(001), thereby reducing the lattice mismatch from 2 .2% to 0.2%. This observation suggests that minimizing the lattice mis match is a key requirement for the growth of high-quality NLO active c halcopyrite structure thin films and is in contrast to some other NLO active thin-film systems.