Double-injection phenomena under magnetic field in SOS films: A new generation of magnetosensitive microdevices

We analyze several sensors belonging to the magnetodiodes family and realized with silicon on sapphire (SOS) technology. They are: p⁺-n-n⁺, Schottky and filamentary magnetodiodes. These very simple devices have "micronic" dimensions compatible with VLSI and exhibit sensitivities which are two orders of magnitude higher than conventional sensors: 30 V/T have been measured on Schottky magnetodiodes without amplification and for low power dissipation. It is shown that the optimum operating as well as the improvement of the device design require conditions of high level injection, corresponding to double-injection phenomena: thus the establishment and the behavior of the so-called "semiconductor regime" have been systematically studied for numerous diodes with different geometries and dopings. Narrowest structures, shorter than 20 µm and with the doping below 10²²m^-3are shown to be suitable. The detailed analysis of different magnetosensitivities is completed with experiments on noise, temperature, and high magnetic field.