Quantitative compositional analysis and strain study of InAs quantum wires with InGaAlAs barrier layers

Quantitative compositional analysis of InAs quantum wires deposited between In0.53Ga0.37Al0.1As barrier layers grown on InP substrates was performed by electron energy loss spectrometry and energy dispersive x-ray spectrometry. An indium-rich region in the center of the wire, with decreasing indium concentration toward the interface with the barrier layers, was observed from indium concentration maps for individual quantum wires. “Stripelike” contrast modulation was observed in diffraction contrast transmission electron microscope images of the In0.53Ga0.37Al0.1As barrier layer immediately above the quantum wires. The contrast originated from indium compositional modulations in the upper barrier layer as confirmed by electron energy loss spectrometry and the modulation is attributed to the presence of an inhomogeneous elastic strain field generated by the buried quantum wires. These results suggest that quantitative analysis of the composition and strain distributions at very high spatial resolution provides insights necessary to further model the physical properties and to understand the growth of these nanostructures.