Hall Coefficient and Magnetoresistance in Semiconducting Diamond

The Hall coefficient and transverse magnetoresistance of two type II-b semiconducting diamonds (p-type) were measured as a function of magnetic field from 500 gauss to 20 000 gauss at fixed temperatures between 0°C and 100°C. These diamonds have R σ values of about 1000 cm 2 v -1 sec -1 at room temperature. The Hall coefficient increases monotonically with increasing field, the total variation being about 10 per cent. This behaviour is similar to that which has been reported for p-type silicon at liquid nitrogen temperature, and it suggests a warped valence band. The transverse magnetoresistance is proportional to H 2 at low fields, but deviates from this behaviour at fields above 4000 gauss. The magnetoresistance is larger than would be expected for a spherical band but can be explained if a warped valence band is assumed. A warped band is also suggested by the longitudinal magnetoresistance which is about one-third the transverse value.