Growth-temperature-dependent band alignment in Si/Ge quantum dots from photoluminescence spectroscopy
2006 (English)In: Physical Review B, ISSN 1098-0121 (print), 1550-235X (online), Vol. 73, no 19, 195319-1--195319-7 p.Article in journal (Refereed) Published
The present work is a photoluminescence study of Si-embedded Stranski-Krastanov Ge quantum dots. The value of the conduction band offset is a result of the magnitude of the tensile strain in the Si surrounding the compressive strained Ge dot. Due to the increased Si/Ge intermixing and reduced strain in the Si barrier, a reduction of the conduction band offset is observed at increased growth temperatures. The optical properties as derived from photoluminescence spectroscopy are correlated with structural properties obtained as a function of the growth temperature. High growth temperatures result in large Ge dots with low density due to the pronounced surface diffusion and Si/Ge intermixing. As confirmed by photoluminescence, the band gap of the Ge dots increases with increased growth temperature due to the higher degree of Si/Ge intermixing. The band alignment is of type II in these structures, but the occurrence of both spatially indirect and spatially direct transitions are confirmed in temperature-dependent photoluminescence measurements with varied excitation power conditions. An increasing temperature results in a gradual transition from the spatially indirect to the spatially direct recombination in the type-II band lineup, due to higher oscillator strength for the spatially direct transition combined with a higher population factor at higher temperatures.
Place, publisher, year, edition, pages
2006. Vol. 73, no 19, 195319-1--195319-7 p.
germanium, silicon, elemental semiconductors, semiconductor quantum dots, semiconductor growth, photoluminescence, conduction bands, internal stresses, surface diffusion, chemical interdiffusion, electron-hole recombination, oscillator strengths
IdentifiersURN: urn:nbn:se:liu:diva-13795DOI: 10.1103/PhysRevB.73.195319OAI: oai:DiVA.org:liu-13795DiVA: diva2:21559
Mats Larsson, Anders Elfving, Wei-Xin Ni, Göran V. Hansson and Per-Olof Holtz, Growth-temperature-dependent band alignment in Si/Ge quantum dots from photoluminescence spectroscopy, 2006, Physical Review B, (73), 195319.
Copyright: American Physical Society