Second-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 second-harmonic generation at a fundamental wavelength of 790 nm. An approximate doubling of the second-order optical nonlinearity of the CuInSe2 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 mismatch is a key requirement for the growth of high-quality NLO active chalcopyrite structure thin films and is in contrast to some other NLO active thin-film systems.