  With an MBE technique, a Si/Ge heterostructures are prepared containing
layers of nanostructured Ge with quantum dots of size of several nanometers.
The effective conductivity of the layers is determined by a quasioptical
terahertz-subterahertz coherent source BWO spectroscopy. The conductivity is
found to be strongly enhanced compared with the conductivity of bulk germanium.
Possible microscopic mechanisms responsible for the enhancement will be
discussed. Application of BWO spectrometers for obtaining precise quantitative
information on of dielectric properties at THz-subTHz frequencies of
semiconducting layers and structures is demonstrated by presenting the
temperature dependences of dielectric characteristics of a commercial silicon
wafer at frequencies 0.3 to 1.2 THz and temperatures 5K-300K.
