TRANSMISSION ELRCTRON MICROSCOPY INVESTIGATIONS OF LOW-PRESSURE CVD GROWTH AND STRAIN RELAXATION OF Ge ISLANDS ON Si（110）

Shapes, dimensions, arrangements and the microstructure of self-assembled islands fabricated by low-pressure chemical vapour deposition (LPCVD) of Ge at 700℃ onto Si(110) substrates have been investigated for different nominal Ge coverage by transmission electron microscopy (TEM) of plan-view and cross-section specimens and have been compared with photoluminescence (PL) measurements of Si-capped layer samples. The transition from the 2-dimensional layer to the 3-dimensional island growth mode takes place for a Ge deposition of nominally less than 2 monolayers. Upon this transition, many coherent islands and few larger islands with extended defects are observed. The coherent islands possess a dome-like shape and lateral sizes up to 130nm. Photoluminescence spectra show island-related peaks whose energy positions are shifted towards lower energy with higher Ge coverage.