CL and Dark Field TEM Analysis of Composition Change at Interfaces in InGaP/GaAs Junctions Grown by MOCVD

Dark field transmission electron microscopy by using both the (200) two beam diffraction mode and the high angle annular dark field (HAADF) method has been used to check the presence and composition of unwanted layer(s), that had formed at the place of the nominal 10 nm thick GaAs QW grown on top of the InGaP barrier in MOCVD InGaP/GaAs samples, and whose existence was suggested by cathodoluminescence. It is shown that the nominal 10 nm GaAs QW has been replaced by 2 layers: a thin one made of In0,15Ga0,85As0,80P0.20 closer to InGaP followed by a second one made of either GaAs0.91P0.09 or In0,05Ga0,95As0,84P0,16.