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.