Influence of the Position of the Fermi Level on an Infrared Active Defect in Irradiated Silicon

Influence of the position of the Fermi level on the infrared active defect, so-called higher order bands (HOB), has been investigated in neutron irradiated silicon by using infrared absorption and Hall-effect measurements at low temperatures. The optical excitation and the introduction of thermal donors (TD) effectively alter the position of the Fermi level. Similar optically active behaviors between the HOB and TD⁺ have been observed. It is suggested strongly that the mechanism of the Fermi level influencing on the HOB is the same as that of the TD⁺.