Excitation-dependent blue shift of photoluminescence peak in 1.5–1.6 µm wavelength region from dislocation-rich Si layers

We study photoluminescence (PL) from dislocation-rich Si layers prepared by Si growth on the nanostructured surface composed of dense arrays of Ge islands grown on the oxidized Si surface. The Si layers exhibit intense PL centered in the 1.5-1.6 wavelength region. The PL is associated with dislocations, which have an extremely high concentration according to transmission electron microscopy data. Using a probable model of electronic structure of dislocated silicon, we assume that the radiative transitions occur between the dislocation-induced conduction sub-band and deep levels located about 0.3 eV above the valence band edge. We found that the dislocation-related PL peak is blue-shifted under high excitation conditions. The shift is considered to be an evidence of carrier transfer between the deep states. We calculate the occupancy of the deep states as a function of the pump power density using the model with non-interacting deep states and find that the occupancy and the PL peak have the similar excitation behavior.