NATURE OF CONDUCTION IN DOPED SILICON

Via ultrafast optoelectronic THz techniques, we are able to test alter native theories of conduction by precisely measuring the complex condu ctivity of doped silicon from low frequencies to frequencies higher th an the plasma frequency and the carrier damping rate. These results, o btained for both n and p-type samples, spanning a range of more than 2 orders of magnitude in the carrier density, do not fit any standard t heory. We only find agreement over the full frequency range with the c omplex conductivity given by a Cole-Davidson type distribution applied here for the first time to a crystalline semiconductor, and thereby d emonstrate that fractal conductivity is not just found in disordered m aterial.