Interpretation of Hall and Photo-Hall Effects in Inhomogeneous Materials

Hall and photo-Hall effects have frequently been used to distinguish between a ``numbers'' mechanism (assumed if Δn ≠ 0 and Δμ = 0), and a ``barier'' mechanism (assumed if Δn = 0 and Δμ ≠ 0) for photoconductivity in possibly inhomogeneous materials. Consideration of a simple model for an inhomogeneous material shows that a wide variety of effects can be obtained in a material with only resistivity variations and without p-n junction barriers. In particular it may be shown that in such a model without barriers, either Δn ≠ 0 and Δμ = 0, or Δn = 0 and Δμ ≠ 0, may be obtained experimentally, depending only on the resistivity ratio between different portions of the material.