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

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 d n / d H 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 k T . In this case we obtain