Integration of Si/Si1-xGex/Si and Si p-i-n diodes with Si nitride optical waveguide on silicon-on-insulator (SOI) substrates has been achieved. For light emission from Si p-i-n diode, photo current of Si/Si1-xGex/Si p-i-n diode is larger than that of Si p-i-n diode, and increases with increasing Si1-xGex layer thickness and Ge fraction. From the relationship between photo current and effective electroluminescence intensity, it is suggested that the enhancement of photo current due to the Si1-xGex layer is caused not only by the narrowing of bandgap but also by the increase of photoelectric conversion efficiency. (c) 2005 Elsevier B.V. All rights reserved.