Micro-Tesla Offset in Thermally Stable AlGaN/GaN 2DEG Hall Plates Using Current Spinning

Abstract

This article describes the characterization of a low-offset Hall plate using the AlGaN/GaN 2-D electron gas (2DEG). A four-phase current spinning technique was used to reduce the sensor offset voltage to values in the range of ∼20 nV, which corresponds to a low residual offset of ∼3.4 ± 2 μ T when supplied with low voltages (0.25–1 V). These offsets are 30x smaller than the values previously reported for GaN Hall plates, and it is on par with state-of-the-art current-spun silicon (Si) Hall plates. In addition, the offset does not exceed 10 μ T even at a higher supply voltage of 2 V. Current spinning was done with a relay matrix at a switching frequency of 1 Hz to enable an offset reduction. The sensor also shows stable current-scaled sensitivity over a wide temperature range of −100 °C to 200 °C, with a temperature coefficient of ∼100 ppm/°C. This value is at least 3x better than the state-of-the art Si Hall plates. Additionally, the sensor's voltage-related sensitivity (∼57 mV/V/T) is similar to that of the state-of-the-art Si Hall plates. Because of the low offset values enabled by current spinning, the AlGaN/GaN 2DEG Hall plates are viable candidates for low-field current and magnetic sensing in high-temperature environments.