ABSTRACT
It is known that, due to its indirect bandgap, Si is an optically inefficient material, although many efforts
have been made in manipulating the materials in order to improve the efficiency. For example, by
incorporating SiGe quantum well layers or self-assembled Ge dots in the Si structure, one can push the
absorption edge into the wavelength range of 1.3 to 1.55mm due to the reduced bandgap [1]. The basic
optical properties cannot be improved, however, since the nature of the indirect bandgap remains for
these materials. In this chapter, we give a summary of the efforts made using another approach, i.e.,
although the materials are not very efficient due to physical limitations, one can instead find new types
of device solutions. Therefore, one can in a more optimized way use the material potential for
fabrication of practically useful Si-based optoelectronics. In this context, three-terminal photonic
devices, namely photonic transistors, are considered. In the following sections, we select several
examples to demonstrate how three-terminal transistors can be implemented for such a purpose of
integrated optoelectronics.
