A method for measuring the Hall mobility in insulating photoconductors is described which avoids the space-charge difficulties present in previous measurements. Unconventional electrodes are used, and the method differs from the conventional one in several other ways. It is a transient method, and the electric field in the sample is rotated by the external electrodes, rather than by the electrons under study. The direction of charge flow is deduced from a current measurement, rather than by confining the current to a thin sample whose orientation gives the direction of charge flow. No attempt is made to inject or eject electrons through the surface of the sample.

Measurements using this technique have been made on a number of diamonds. Both electrons and holes are found to contribute to the photoconductivity, making interpretation of the data difficult. It is tentatively concluded that the electronic mobility varies as $T^{-\frac{3}{2}}$ and is about 1800 ${\mathrm{cm}}^2$/volt-sec at 300°K. For holes it is concluded (with far less certainty) that the mobility also varies as $T^{-\frac{3}{2}}$ and is somewhat greater than 1200 ${\mathrm{cm}}^2$/volt-sec at 300°K. These observations are consistent with the deformation potential theory of electronic mobility in nonpolar crystals.

• Received 19 January 1954

DOI:https://doi.org/10.1103/PhysRev.94.526