Full three-dimensional numerical analysis of multi-collector magnetotransistors with directional sensitivity

We have studied the operation of multi-collector bipolar transistors with directional magnetic-field sensitivity. The complex three-dimensional (3D) device consists of four crosswise-arranged lateral transistors with one common central emitter. To analyse the electrical characteristics and sensor performance, we have modelled the complete device structure using technological and physical parameters extracted from experimental measurements on real devices. Because of the complex geometry, a full 3D numerical analysis of carrier flow and electrostatic potential is required in order to study the effects of an arbitrarily oriented magnetic field. A simplified analysis confined to the 2D central mirror plane is inadequate even for the mere electric device behaviour at zero magnetic field. This reflects the problem of current calibration inherent in 2D approximations of devices with widely differing contact areas. To overcome this discrepancy, we have implemented for the first time the 3D galvanomagnetic transport vector equations in a state-of-the-art general-purpose device simulator.