Optical second harmonic imaging: a versatile tool to investigate semiconductor surfaces and interfaces

¹ Laser Research Institute, Physics Department, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa
² Institut für Physikalische Hochtechnologie (IPHT), POB 100239, D-07702 Jena, Germany

Corresponding author: tscheidt@physics.sun.ac.za

Received: 4 July 2003
Accepted: 18 December 2003
Published online: 15 July 2004

Abstract

Optical second harmonic (SH) imaging using femtosecond laser pulses (782 nm, 80fs) is applied to investigate the structural quality of SiC and ZnO thin films grown by chemical vapour deposition (CVD) on Si(100) substrates. We find a spatially uniform SH response from the SiC sample as well as a regular 4-fold symmetry (3C-SiC-(001)) in the rotational SH anisotropy. The ZnO film is poly-crystalline as indicated by a strongly position dependent SH response and the missing regularity in the rotational SH anisotropy. The estimated grain size is ~ 30−50 µm. Furthermore our time dependent SHG measurements on native Si/SiO₂ for laser peak intensities up to 100 GW/cm² indicate that hole injection and trapping into the ultrathin SiO₂ layer contributes to the SH signal above  GW/cm². The SHG images of defects irreversibly induced in Si/SiO₂ under laser irradiation are reproduced by scanning electron microscopy (SEM).