Carrier gas effects on the SiGe quantum dots formation

Abstract

SiGe quantum dots (QDs) grown by ultra-high vacuum chemical vapor deposition using H(2) and He carrier gases are investigated and compared. SiGe QDs using He carrier gas have smaller dot size with a better uniformity in terms of dot height and dot base as compared to the H(2) carrier gas. There is a higher Ge composition and less compressive strain in the SiGe QDs grown in He than in H(2) as measured by Raman spectroscopy. The Ge content is higher for He growth than H(2) growth due to hydrogen induced Si segregation and the lower interdiffusivity caused by the more strain relaxation in the He-grown SiGe dots. The photoluminescence also confirms more compressive strain for H(2) growth than He growth. Hydrogen passivation and Ge-H cluster formation play an important role in the QDs growth. (C) 2008 Elsevier B. V. All rights reserved.