Quantum-confinement effects in InAs-InP core-shell nanowires

We report the detection of quantum confinement in single InAs-InP core-shell nanowires. The wires, having an InAs core with ∼25nm diameter, are characterized by emission spectra in which two peaks are identified under high excitation intensity conditions. The peaks are caused by emission from the ground and excited quantized levels, due to quantum confinement in the plane perpendicular to the nanowire axis. We have identified different energy contributions in the emission spectra, related to the wurtzite structure of the wires, the strain between the wurtzite core and the shell, and the confinement energy of the InAs core. Calculations based on six-band strain-dependent theory allow the theoretical estimation of the confined energy states in such materials, and we found these results to be in good agreement with those from the photoluminescence studies.