Hall effect hopping conduction

This same equation is, of course, also used to rationalise the general electronic behaviour of metals, semiconductors and insulators. The quantitative application of Eqn (2.1) is handicapped for ionic conductors by the great difficulty in obtaining independent estimates of c,- and u,-. Hall effect measurements can be used with electronic conductors to provide a means of separating c, and u,- but the Hall voltages associated with ionic conduction are at the nanovolt level and are generally too small to measure with any confidence. Furthermore, the validity of Hall measurements on hopping conductors is in doubt. 

The Hall effect for hopping conduction is discussed in Chapter 5. 

The Hall effect in the temperature range where conduction is by variable-range hopping is not well understood. Evidence from the early work by Fritzsche is discussed by Shklovksii and Efros (1984), who come to the conclusion that the Hall mobility must be small. Hopkins et al (1989) have investigated the behaviour of heavily doped Ge Sb, pushed into the non-metallic regime by magnetic fields up to 7 T, at temperatures down to 100 mK. Below 1 K the... 

The implant surface has a large resistivity and a large temperature coefficient of resistance (TCR), as shown by the data in Fig. 6. In addition, a large number of carriers is indicated by measurements of the Hall effect (>10 cm" ) [7]. These results imply that the mobility of the carriers must be very small. The low mobility can be attributed to a disorder-limited, hopping, conduction process, where the carriers are thermally activated into conduction states [9]. 

Figure 19 Mobility of carriers in P-rhombohedral boron obtained by different methods and different authors. 1, From space-charge limited currents 2 and 3, (1h 4, field effect 6, thermally activated hopping O, from electrical conductivity and spin density , (Xh. > from electrical conductivity and ESR magnetoresistance , from ESR line width +, band mobility A, hopping mobUity A, from photoconductivity V, from high-field conductivity, I, Hall mobility and photoconductivity. (See Ref. 2 and references therein.)...

---