Rotation of base region hall field in magnetotransistors

Abstract

We present measurement results of Hall field rotation in the base region of npn lateral magnetotransistors operated in common base configuration at various emitter currents. The measured Hall voltages are small ( V H ∼μV) and the direction of the corresponding Hall field progressively rotates with increasing collector bias voltages, V CB . In terms of device parameters, the Hall fields were found to behave in the following manner. In the regime where the common base current gain h FB <1, the Hall field is relatively large (due to the high base current) and is mainly due to majority carriers. Beyond a certain critical V CB where h FB ⩾1, the Hall field saturates to some finite value for a given emitter current and is opposite in direction. Its Hall coefficient is opposite in sign and is due to the excess minority charge injected into the base (n ≳ p). The switch in sign happens where h FB ≲ 1 when n ≳ p (μ p */μ n *) 2 in the base region.