  This letter describes the characterization of a low-offset Hall-effect plate
using the AlGaN/GaN two-dimensional electron gas(2DEG). Four-phase current
spinning was used to reduce sensor offset voltage to values in the range of 20
nV, which corresponds to a low residual offset of 2.6 micro-Tesla when supplied
with low voltages (0.04 to 0.5V). These offsets are 50x smaller than the values
previously reported for GaN Hall-effect plates, and it is on par with
state-of-the-art silicon Hall-effect plates. In addition, the offset does not
exceed 10 micro-Tesla even at higher supply voltage of 2.34V. The sensor also
shows stable current-scaled sensitivity over a wide temperature range of -100C
to 200C, with temperature drift of -125 ppm/C. This value is 3x better than
state-of-the-art Silicon Hall-effect plates. Additionally, the sensor's voltage
sensitivity (57 mV/V/T) is also similar. Because of their low offset values,
AlGaN/GaN Hall-effect plates are viable candidates for low-field and high
temperature magnetic sensing in monolithic GaN systems used in extreme
temperature environments such as power inverter, down-well, combustion, and
space applications.
