  The current- and voltage-scaled sensitivities and signal-to-noise ratios
(SNR) (with respect to thermal noise) of various octagonal AlGaN/GaN and
InAlN/GaN Hall-effect sensors were examined in this work. The effect of metal
contact lengths on sensitivity and sensor offset was evaluated. Calculations
that take into account the shape of the device show that devices with
point-like contacts have the highest current-scaled sensitivity (68.9 V/A/T),
while devices with contacts of equal length to their non-contact sides have the
highest voltage-scaled sensitivity (86.9 mV/V/T). The sensitivities of the two
other devices follow the predicted trends closely. All the devices have offsets
less than 20 $\mu$T at low supply current operation (< 300 $\mu$A) and most
remain below 35 $\mu$T at higher supply current (up to 1.2 mA). The consistent
low offsets across the devices imply that the choice of Hall-effect sensor
geometry should mainly depend on whether the device is current-biased or
voltage-biased and the frequency at which it will operate. This work
demonstrates that GaN Hall-effect sensor performance can be improved by
adjusting the geometry of the Hall-effect plate specific to its function (e.g.,
power electronics, navigation, automotive applications).
