Microwave Harmonic Generation in Semiconductors at Low Temperatures. II. Silicon

A resonance type third harmonic generation (THG) in a magnetic field is observed in n -type silicon under illumination at liquid helium temperatures as in the case of n -type germanium (T. Kamiya et al. : J. Phys. Soc. Japan 27 (1969) 679). A photo-response of the THG is investigated in detail, and the THG shows complicated decay below 2°K after the illumination. This shows that the resonance type THG arises from the multiphoton resonance of electrons in very shallow trapping states. A phenomenological analysis of the complicated dacay is made based on a model, in which there are two series of energy levels in the trapping center, and the thermal ionization energies are obtained to be .63±0.13 meV and 0.42±0.07 meV for each ground state. This result seems to indicate that the obsorved trapping center is attributed to the donor negative ion (D - ). Another experiment on thermally stimulated current (TSC) in n -type silicon is carried out below 1°K, and the depth of the trapping state obtained is almost the same as that observed in the THG experiment.