Decomposition analysis of GaxIn1-xAsyP1-y heterostructures by STEM

GaxIn1-xAszP1-z/GayIn1-yAszP1-z multi quantum wells and GaxIn1-xAsyP1-y single layers grown by MOVPE were investigated by STEM using bright-field and atomic number (Z-) contrast imaging, PEELS and CBED. GaxIn1-xAsyP1-y layers on different substrate orientations and of different chemical compositions were compared in the context of their location in the plot of the miscibility gap. The use of misoriented substrates intensifies the decomposition phenomena. For the case of strong Z-contrast variations we determined the local chemical composition of the decomposed phases by PEELS using a 0.5 nm probe. The variations of x and y were Delta x=0.02 and Delta y=0.04, respectively. These results were confirmed by CBED strain measurements. The influence of pressure and temperature in MOVPE is discussed.