Sign of the Hall Coefficient in a Relaxation-Case Semiconductor

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Abstract
In a relaxation‐case semiconductor the dielectric relaxation time exceeds carrier diffusion‐length lifetime, and the neutrality condition no longer holds. It is shown that the sign of the Hall coefficient in a p‐type relaxation‐case material is positive, if the hole density exceeds the electron density times the square of the mobility ratio. This relation is identical to the one for conventional lifetime‐case materials, but has here been derived without assuming neutrality. Practical Hall‐effect measurements with relaxation‐case samples may, however, be seriously altered by space‐charge effects. We describe one case where a negative Hall coefficient always results regardless of the initial doping; this situation may be related to the ``Hall‐effect/Seebeck‐effect anomaly'' in amorphous films.