High quality, relaxed SiGe epitaxial layers for solar cell application

Epitaxially grown, relaxed Si1-xGex layers with x less than or equal to 0.1 were grown on a Si (100) substrate by means of reduced pressure chemical v apor deposition at a temperature of 750 or 800 degrees C. The analysis carr ied out on the grown layers revealed a very high material quality indicated by the low density of dislocations (10(5) cm(-2)) and the high diffusion l ength which was deduced from the measurements of electron beam induced curr ent (EBIC) performed on the as-grown layers. Transmission electron microsco py (TEM) measurements showed that the threading dislocation segments do not extend inside the layer but an rather confined to the Si/SiGe interface, w hich results in a low density of dislocations in the material. The processe d solar cells made from these SiGe layers showed a higher infrared response than those made of a corresponding Si grown and processed under similar co nditions. No degradation of the solar cell performance caused by the disloc ations in the SiGe layers has been observed. (C) 1999 Elsevier Science S.A. All rights reserved.