  Topological Insulator-based devices can transport electrons/photons at the
surfaces of materials without any back reflections, even in the presence of
obstacles. Topological properties have recently been studied using
non-reciprocal materials such as gyromagnetics or using bianisotropy. However,
these effects usually saturate at optical frequencies and limit our ability to
scale down devices. In order to implement topological devices that we introduce
in this paper for the terahertz range, we show that semiconductors can be
utilized via their cyclotron resonance in combination with small magnetic
fields. We propose novel terahertz operating devices such as the topological
tunable power splitter and the topological circulator. This work opens new
perspectives in the design of terahertz integrated devices and circuits with
high functionality.
