Phenomenological Theory of Turnover in Point-Contact Rectifiers

抄録

Turnover relations associated with the general class of the isothermal current-voltage characteristics of the form I=A(T)Vⁿexp [−f(V)⁄kT] have been derived generally by using contact temperature T_c as T_c=T_a·exp (P⁄2πrξ) and the turnover condition (∂V⁄∂T_c)_Tc=0, where T_a is the ambient temperature, P the rate of power generation in a barrier, ξ⁄T the thermal conductivity of a semiconductor, r the radius of a whisker tip. According to the results of the numerical calculations of the turnover relations, using the modified isothermal diode theory taking into account minority carriers (generated by intrinsic condition) as one kind of thermal equilibrium approximation and assuming the effect of image force and a Mott barrier, it was found that the above type of isothermal characteristics could not only lead to the essential features of the observed turnover behaviour that both turnover power and voltage decrease with increasing ambient temperature, but also agrees fairly well with the experimental results on germanium point-contact rectifiers obtained by Benzer. The simple isothermal diode theory taking into account majority carriers only can also lead to the essential features of the turnover behaviour although agreement between the theory and the experiment is very poor. From considerations of the rectification mechanism of the above mentioned modified isothermal diode theory, it was found that minority carriers, as well as majority carriers, played an important role in the turnover behaviour.