Temperature, Sensitivity, and Frequency Response of AlN/GaN Heterostructure Micro-Hall Effect Sensor

We report for the first time on an aluminum nitride/gallium nitride (AlN/GaN) heterostructure as a microscale Hall effect sensor for current sensing applications in extreme environments. The AlN/GaN devices demonstrated high signal linearity as a function of the magnetic field across a temperature range from $-$ 193 $^{\circ}$ C to 407 $^{\circ}$ C. The measured room temperature (RT) supply voltage-related sensitivity ( $\textit{S}_{\text{svrs}}\text{)}$ and supply current-related sensitivity ( $\textit{S}_{\text{scrs}}\text{)}$ are 0.055 T $^{-\text{1}}$ and 32 VA $^{-\text{1}}$ T $^{-\text{1}}$ , respectively. The supply power-related sensitivity ( $\textit{S}_{\text{sprs}}\text{)}$ is 1.4 VW $^{-\text{1}}$ T $^{-\text{1}}$ above 40-mW input bias, which is higher than that of the Al $_{\text{0}.\text{2}}$ Ga $_{\text{0}.\text{8}}$ N/GaN device. The designed AlN/GaN micro-Hall sensor is further determined to have a lower power consumption and higher temperature sensitivity than equivalent Al $_{\text{0}.\text{2}}$ Ga $_{\text{0}.\text{8}}$ N/GaN Hall devices. When operated in an ac bias mode, the rise time of the Hall sensor was found to be 102 ns, corresponding to a frequency bandwidth of 9.8 MHz. We also observed a phase shift between an applied magnetic field and the Hall sensor signal, which can potentially be helpful to monitor ac line currents.