High temperature Hall effect sensors based on Al Ga N ∕ Ga N heterojunctions

We report on Al Ga N ∕ Ga N heterojunction structures for use in Hall effect sensors working over a wide range of temperatures. Room temperature current-related magnetic sensitivity of 55 V ∕ A T at a sheet resistance below 300 Ω ∕ sq and very low temperature cross sensitivity of 103 ppm ∕ ° C up to 300 ° C were obtained for a square-shaped Hall effect sensor. The active layer of the Hall effect sensor is the two-dimensional electron gas formed at the Al 0.3 Ga 0.7 N and GaN heterointerface caused by the gradient in the total polarization between the AlGaN barrier and the GaN buffer layer, which results in the positive polarization induced interface charge attracting free electrons. The temperature-dependent transport properties of the heterojunction were analyzed by Hall measurement. The drop of its electron mobility from room temperature to 300 ° C is mainly due to the enhanced polar optical scattering, while the very stable sheet carrier density contributes to the excellent temperature cross sensitivity of the Hall effect sensor.