Photoluminescence study of the initial stages of island formation for Ge pyramids/domes and hut clusters on Si(001)

Stranski–Krastanov growth of Ge on Si(001) can result in various different types of islands such as domes, pyramids, and hut clusters. A systematic study of the impact of the different island phases on photoluminescence (PL) spectra is presented and reveals simultaneous PL from the wetting layer and islands in the pyramids/domes phase and only island related PL in the phase of hut clusters. A rather abrupt transformation from pyramids/domes to hut clusters is reported by changing the growth temperature from 600 to 580 °C. The wetting layer and island related energy transitions as a function of Ge coverage are presented for growth temperatures ranging from 360 to 700 °C. At $T_s\text{=360\hspace{0.05em}°}\mathrm{C}$ no island formation is present. The influence of Oswald ripening and material interdiffusion on the PL properties is discussed.