Double carrier deflection high sensitivity magnetic sensor

Abstract

Apparatus for a bipolar active semiconductor magnetic field sensor that has a higher sensitivity than semiconductor field sensors presently existing in the art. Specifically, the inventive sensor utilizes a semiconductor structure containing a single emitter layer, a single base layer that is overlaid over the emitter layer and two separate oppositely situated collectors located above the base layer. A bias lateral majority carrier flow is established, in preferably and respectively both the base and emitter layers (electrons in the emitter, holes in the base), that flows in opposite directions in these layers and is oriented normal (transverse) both to the direction of transistor current and to the direction of a magnetic field that is to be detected. When the magnetic field is applied to the sensor, this field imparts a Lorentz force to these carriers which causes these majority carriers to deflect in the same direction in both the emitter and base layers, respectively. The resulting deflection of these carriers, in turn, produces local Hall effect voltages, that are proportional to the strength of the magnetic field, across the emitter-base junction that locally increases the forward bias of this junction near one collector and locally decreases the forward bias of this junction near the other collector so as to exponentially increase the collector current flowing through one collector while exponentially decreasing the collector current flow through the other collector. Inasmuch as the exponential collector current flow is a very sensitive function of emitter-base voltage, the inventive sensor is substantially more sensitive than semiconductor sensors known in the art.