The influence of molecular hydrogen (H-2) on the structural and optical pro
perties of self-assembled Ge dots grown on Si(001) has been studied using a
tomic force microscopy and photoluminescence spectroscopy (PL). Without hyd
rogen, a well known bimodal island size distribution occurs with small {105
} faceted pyramids, and larger multifaceted domes. In the presence of an ad
ditional H-2 flow, we observe that a higher density of smaller pyramids and
a lower density of domes occurs. Moreover, in the presence of hydrogen, PL
investigations have revealed a thicker wetting layer thickness, probably d
ue to a reduction of the surface diffusion length. (C) 2000 American Instit
ute of Physics. [S0021-8979(00)07822-1].