Electrical characterisation of local electronic properties of self-assembled semiconductor nanostructures using AFM

Scanning capacitance microscopy (SCM) and Kelvin probe force microscopy (KPFM) have been used to characterise self-assembled Ge nanoislands embedded in silicon. High contrast in capacitance and in surface potential are found between areas with nanostructures and areas without any nanostructures. The local dC/dV spectroscopy shows flat band voltage shift attributed to the presence of electric charges in the nanostructures. The KPFM contrast has been correlated with the band structure offsets between the nanostructure and the matrix barrier. Effects of the charging have been measured from the dC/dV curve and discussed in terms of the wetting layer influence that contributes to the escape of the charges when percolation of charges is observed.