Finite-element analysis of magnetotransistor action

Most of the semiconductor device geometries that are being experimented with for improved magnetic field sensing do not lend themselves to accurate analytical modeling. The vectorial interaction taking place between the electrical current and the magnetic field complicates the problem of solving nonlinearly coupled carried density and electrostatic potential equations. In this work, solutions to the carrier density and electrostatic potential distributions are obtained by using a finite-element technique for a structure representing lateral and vertical bipolar transistors with multiple collectors. The results presented show the effect of the magnetic field to be very nonuniformly distributed around the emitter with a heavy-concentration near the emitter edges where the Lorentz-force-driven carriers are stopped at the insulating boundaries and give rise to a magnetoconcentration in the carrier densities. Distribution of currents collected by a multitude of collectors surrounding the emitter and their sensitivity to the magnetic field are given. The vertical magnetosensitivities are found to be an order of magnitude smaller than the lateral magnetosensitivity because of the lack of such a magnetoconcentration of carriers under the emitter. The computer program developed can simulate unipolar as well as bipolar magneto-sensitive devices with any boundary geometry