Electroluminescence and photoluminescence of Si/SiGe self-assembly quantum dot structures

Comparative electroluminescence (EL) and photoluminescence (PL) measurements were performed on Si/Si0.6Ge0.4 self-assembly quantum dots (QDs) structures. The samples were grown pseudomorphically by molecular beam epitaxy, and PIN diodes for electroluminescence were fabricated. Assisted TEM pictures shows the SiGe self-assembly QDs are plate-like. And it showed that the diameters of QDs are in range from 40 nm to 140 nm with the most in 120 nm. Both EL and PL has a wide luminescence peak due to wide distribution of QDs dimensions. At low temperature (T equals 14 K), EL peak has a red shift compared to the corresponding PL peak. Its full-width at half- maximum (FWHM) is about 97 meV, a little smaller than that of corresponding PL peak. The reasons of position and FWHM changes of EL peak from QDs have been discussed.