TIME DEPOSITION DEPENDENT SURFACE MORPHOLOGY AND PHOTOLUMINESCENCE OF Ge NANOISLANDS

Ge/Si nanoislands having width lies between ~ 55 nm to 85 nm and the height ranges from ~ 6 nm to ~ 21 nm are fabricated using radio frequency (RF) magnetron sputtering deposition technique. The growth kinetics, surface morphology and optical behavior of Ge islands are characterized employing energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM) and photoluminescence (PL). The occurrence of the photoluminescence peaks at around 3.29 and 2.85 eV are interpreted to Ge islands and Ge-O interface reaction. The red shift (0.28 eV) for the PL peak position that occurs with changing the islands size is attributed to the effect of quantum confinement. The RMS roughness and number density of islands found to be strongly influenced by deposition time. The minimum of RMS roughness and the maximum of the number density occurred for deposition time 300 sec and 180 sec respectively. The mechanism of size variation of Ge islands with deposition time is analyzed and understood