TRANSMISSION ELECTRON-MICROSCOPY AND SCANNING-TRANSMISSION ELECTRON-MICROSCOPE ANALYSIS OF THE EFFECTS OF THERMAL-PROCESSING ON THE STRUCTURAL INTEGRITY OF GAINAS GAINASP MULTILAYERS/

The structural characterization by electron microscopy of a metalorgan ic chemical vapor deposition grown GaInAs/GaInAsP multiple-quantum-wel l structure undergoing a ''blue shift'' in luminescence wavelength upo n thermal processing, as part of a multistage epitaxial growth process , is reported. The sample exhibits a shift toward shorter wavelengths of greater than 100 nm upon annealing at 750-degrees-C. The structural modifications that result in the blue shift include an elimination of atomic ordering in the quaternary barrier layers of the material, and significant layer interdiffusion. A method is described whereby quant itative analyses of the layer composition and lattice parameter with a spatial resolution better than 2 nm can be obtained from semiconducto r multilayers using energy-dispersive x-ray microanalysis in the scann ing transmission electron microscope. Such an analysis shows that the interdiffusion occurs along a nonlinear (that is, nonlattice matched) path where the group-V element diffusivities exceed those of the group -III elements, and results in the incorporation of excess coherency st rains of up to 0.5% in the quantum-well regions.