Narrow-gap semiconductor magnetic field sensors and applications

Narrow-gap semiconductors have been used for decades in the fabrication of magnetic field sensors, such as magnetoresistors and Hall sensors. Magnetic field sensors are, in turn, used in conjunction with permanent magnets to make contactless potentiometers and rotary encoders. This sensing technology offers the most reliable way to convert a mechanical movement into an electrical signal, and is widespread In automotive applications. semi-insulating GaAs or InP substrates have resulted in the development of magnetoresistors with excellent sensitivity and operating temperatures up to 285%. Magnetoresistors and Hall sensors require a very thin active semiconductor region, a high carrier density and a high room-temperature mobility. The best materials are narrow-gap l lCV compounds. 2DEG layers in InSb and lnAs would be ideally suited for these devices. The,accumulation layer at t h e surface of InAs has been used to make magnetoresistors. Hall sensors and magnetotransistors. n-type doped thin lnSb films are used to make magnetoresistors that outperform Si-based Hall sensors, even with integrated amplification. We describe device design criteria, materials requirements and a direct comparison of the three types of galvanomagnetic devices, magnetoresistors. Hall sensors and magnetotransistors, made from the same material. We compare the output of different magnetic field sensing technologies, such as Si and GaAs Hall sensors, and NiFe-based magnetoresistors, with lnSb magnetoresistors. Recent developments in the growth of thin epitaxial layers of InAs and inSb on