IN-SITU DETERMINATION OF INPLANE STRAIN ANISOTROPY IN ZNSE(001) GAAS LAYERS USING REFLECTANCE DIFFERENCE SPECTROSCOPY/

In this article we show in situ and ex situ experimental reflectance d ifference spectroscopy (RDS) data of ZnSe(001) grown on GaAs, where sp ecial attention is focused on the resonancelike structure at the band gap of ZnSe. This feature was reported previously and interpreted as e ither the transition from the valence band of ZnSe to a quantum well s tate at the ZnSe/GaAs interface or it was attributed to interface stat es. We report a new interpretation of this spectral feature which cons iders anisotropic strain in the ZnSe/GaAs heterostructures. By straini ng the ZnSe(001) epilayers mechanically, it was observed that the reso nance feature changed sign and magnitude, proving that the height of t his in-plane anisotropy feature is a measure for the in-plane strain. In-plane strain induces a splitting and shift in energy of the light a nd heavy hole; valence bands. The transition between the light hole va lence band and the conduction band is not polarization dependent, howe ver the transition between the heavy hole valence band and the conduct ion band, as well as the transition between the spin split-off band an d the conduction band shows polarization dependence. This difference b etween the reflectances parallel and perpendicular to the in-plane str ain direction can be measured ex situ and in situ with RDS. (C) 1998 A merican Vacuum Society.