Infrared spectroscopy of self-organized InAs nanostructures grown on InAlAs/InP(0 0 1) for infrared photodetection applications

InAs nanostructures on InAlAs/InP(001) have been fabricated using Stranski-Krastanov growth mode. Depending on growth conditions, a full coverage of the InAlAs surface by either InAs quantum wires or quantum dots can be achieved. Giant intraband absorptions are observed at mid-infrared wavelengths. The intraband resonances are strongly polarized in the layer plane as a consequence of the quantum confinement along the [110] direction. The absorption at normal incidence reaches 26% for 10 layers of n-doped (1×10¹²cm^-2) InAs elongated dots. We also report on femtosecond pump-probe experiments aimed at measuring the electron capture time. Typical times range from 3 ps for broad wires to 6 ps for narrow wires.