The Change of Carrier Concentration in the Simple Semiconductors with Static Magnetic Field

概要

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The change of carrier-concentration with static magnetic field is discussed by using the simple model of the semiconductors. The attention is mainly focused on whether the concentration of free carriers increases or decreases with the field. The situations are classified into three cases [A], [B] and [C] according to the degree of concentration of the centers. [A] The concentration of the trapping centers is dilute and a center can trap only one carrier. In this case the carrier concentration n is a monotonously decreasing function of the field H, namely dn/dH^2≧0, [B] The impurity levels lose the locality and form a band so called "impurity band," however, the width of which is still smaller than κT. In this case we obtain (dn/dH^2)_<weak H> > 0 when (m/m^*) < √<3δ> (dn/dH^2)_<weak H> < 0 when (m/m^*) < √<3δ> where m^* is the effective mass of carriers and δ means the degree of compensation, namely δ = (N_d -N)/Nd. [C] The width of impurity band is larger than κT and the Fermi-level ζ_0 at H = 0 lies in this band. In this case we obtain (dn/dH)_<weak H> > 0 when (m/m^*) < √<3(1-δ)> where δ = κT[〓/(〓E)logD(E)]_<E-ζ_0> D(E) means the state density of the impurity band. It seems that there is no possibility to explain the so-called "magneto-conductive" phenomena observed in p-InSb from this stand-point.
社団法人日本物理学会の論文
1958-04-05