| Popis: |
The low-temperature data of Hall-effect measurements on n-type InP samples have been analyzed on the basis of an impurity-Hubbard-band model with taking into account the temperature dependence of the Hall factor for hopping conduction in impurity Hubbard bands. As for the hopping conduction mechanism, we assumed nearest-neighbor hopping (NNH) in the top Hubbard band (D- band) while assumed variable-range hopping (VRH) in the bottom Hubbard band ( $\mathrm{D}^{0}$ band). The activation energy $\epsilon_{2}$ for NNH conduction in the D- band has been deduced and is shown to obey the relation of $\epsilon_{2}\propto(\mathrm{d}_{\mathrm{ND}}-\mathrm{d}_{0\mathrm{cr}})^{1/3}$ , where $\mathrm{d}_{\mathrm{ND}}$ is the average net donor separation, $\mathrm{d}_{0\mathrm{cr}}$ is its critical value at which the metal-insulator transition occurs, and K is the compensation ratio. The Hall coefficient as well as the Hall mobility in the temperature range of 8–25 K, in which the Hall coefficient has its maximum, is shown to be dominated by the $\epsilon_{2}$ conduction in the D- band. The characteristic temperature of the Mott VRH in the $\mathrm{D}^{0}$ band has been deduced and is shown to be decrease with the donor concentration. |
