Response of elementary semiconducting structures to a terahertz electric field

With a bulk plasma frequency in the terahertz range, extrinsic semiconductors may be employed to form composites with tailored dispersion characteristic for fabrication of passive components in the terahertz band. Computations have been performed to study the polarization process in nanoscale semiconducting plates and spheres, employing a transport formulation to account for space charge effects. Results reveal a frequency dependent dipole moment that is influenced by the carrier density when it reaches the level of 10¹⁶ cm^-3 and a size dependence as the characteristic length in field screening by the space charge is approached. To obtain higher contrast in dispersion effects resulting from the polarization of mobile charges, a material with lower intrinsic permittivity is preferred for developing composites with dispersion properties that are adjustable by composition variation and synthesis processes.