| Abstract: |
Hall-effect sensors are widely used in the automotive industry, in power electronics, and within inertial measurement units (IMUs) for navigation and position sensing. There is a growing need for Hall-effect sensors that can operate under extreme conditions, specifically in high temperature environments such as deep underground (e.g., well-logging) and in outer space. Electronic components, including Hall-effect sensors, are typically made of silicon, but these components begin to breakdown at temperatures beyond 200°C, and thus external cooling is often required. However, implementing external cooling processes necessitates additional power and contributes further bulk and complexity to the system, leading to increased size, weight, and overall costs of the system. Thus, components that can operate at extreme temperatures without additional cooling are necessary for achieving higher efficiency, higher reliability, and lower cost. Wide bandgap semiconductors such as gallium nitride (GaN) and aluminum nitride (AlN) have been shown to operate up to 1000°C in vacuum and thus are a prime candidate for electronics in harsh environmental conditions.
We have developed GaN-based Hall-effect sensors with high sensitivity (similar to commercial silicon devices) and extremely low offsets. We characterized their voltage- and current-scaled magnetic sensitivities between room temperature and 600°C. Both devices showed decreasing voltage-scaled sensitivity at high temperature, 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 ~10% from their mean, due to a minimal dependence of sheet carrier concentration on temperature. 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, a sample held at 576°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. |