This paper is the review of our study published earlier in Acta Phys. Polon. A 121, 522 (2012) [7], Phys Lett A 378, 1364 (2014) [25], and [1]. It’s aim is to pay attention to the new possibilities related to producing the new types of THz generators. The suggested effects are the result of combining two effects: Gunn-effect in a material such as GaAs and undulator-like radiation, or 'pumping wave' acting on the electrons which is the result of undulator field, while the second is the backward effect of radiation which is produced by electrons moving within such a micro-undulator. It is very probable that the effects can be used to develop a new semiconductor-based room temperature source of the THz-radiation.