Nanocrystals Grown on a Surface of Si, Ge and SiGe/Si Crystals Stimulated by Laser Radiation

Abstract

The aim of this work is to study the mechanism of nanohills growth in SiGe/Si structure by laser radiation. P-type Si (001), i-type Ge crystals and SiGe/Si heteroepitaxial structure were irradiated by nanosecond Nd:YAG laser pulses. Nanocrystals are grown on the irradiated surface of Si, Ge crystals and SiGe/Si heteroepitaxial structure at intensity of the laser radiation up to 2MW/cm2, 20MW/cm2 and 25MW/cm2, respectively. Self-organized structures are observed and characterized. For example, they show a strong photoluminescence in the visible range of spectra with long wing in the red part of spectra which can be explained by quantum confinement effect in nanocrystals-nanowires with graded diameter. An evidence of this effect is the red shift of Ge-Ge phonon line at 300 cm-1 in micro-Raman spectra. Thus we have found a new method for the growth of semiconductor nanocrystals with graded band gap due to quantum confinement using laser radiation of an elementary semiconductor