High quality, relaxed SiGe epitaxial layers for solar cell application

摘要

Epitaxially grown, relaxed Si_(1-x)Ge_x layers with x ≤ 0.1 were grown on a Si (100) substrate by means of reduced pressure chemical vapor deposition at a temperature of 750 or 800 °C. The analysis carried 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 length which was deduced from the measurements of electron beam induced current (EBIC) performed on the as-grown layers. Transmission electron microscopy (TEM) measurements showed that the threading dislocation segments do not extend inside the layer but are rather confined to the Si/SiGe interface, which results in a low density of dislocations in the material. The processed solar cells made from these SiGe layers showed a higher infrared response than those made of a corresponding Si grown and processed under similar conditions. No degradation of the solar cell performance caused by the dislocations in the SiGe layers has been observed.