  The magnetic sensitivity of Hall-effect sensors made of InAlN/GaN and
AlGaN/GaN heterostructures was measured between room temperature and
576{\deg}C. Both devices showed decreasing voltage-scaled magnetic sensitivity
at high temperature, declining from 53 to 8.3 mV/V/T for the InAlN/GaN sample
and from 89 to 8.5 mV/V/T for the AlGaN/GaN sample, corresponding to the
decreasing electron mobility due to scattering effects at elevated
temperatures. Alternatively, current-scaled sensitivities remained stable over
the temperature range, only varying by 13.1% from the mean of 26.3 V/A/T and
10.5% from the mean of 60.2 V/A/T for the InAlN/GaN and AlGaN/GaN samples
respectively. This is due to the minimal temperature dependence of the electron
sheet density on the 2-dimensional electron gas (2DEG). Both devices showed
consistency in their voltage- and current-scaled sensitivity over multiple
temperature cycles as well as nearly full recovery when returned to room
temperature after thermal cycling. Additionally, an AlGaN/GaN sample held at
576{\deg}C for 12 hours also showed nearly full recovery at room temperature,
further suggesting that GaN-based Hall-effect sensors are a good candidate for
use in high temperature applications.
