Fast Hall™: A method for high speed AC field, AC current Hall measurements.

The Hall effect, discovered in 1879 by E. Hall, is the primary method to measure carrier density, mobility and carrier type in materials. The most common method for measuring the Hall effect in semiconductors uses a DC magnetic field. This method depends are reversing the direction of the magnetic field. For some applications, especially low mobility materials, the use of an AC field instead of a DC field provides better measurements. Using the field reciprocity theorem, it is possible to generate the same hall measurements without the use of an external AC field. The frequency of this “effective AC field” is determined by the rate of interchanging the current and voltage leads attached to the sample and is not limited by the induction of the magnet generating the DC field. The current excitation can also be modulated by switching the direction of the current leads. The frequency of the effective AC field and the AC current do not have to be the same. This provides the opportunity of dual frequency (AC field/AC current) hall measurements over a wide, and independent, frequency range. Measurements of low mobility (< 1 cm²/(V s) materials will be presented.