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Analysis of Variable-Range Hopping Conductivity in Si : P

✍ Scribed by M. Hornung; M. Iqbal; S. Waffenschmidt; H. v. Löhneysen

Publisher
John Wiley and Sons
Year
2000
Tongue
English
Weight
215 KB
Volume
218
Category
Article
ISSN
0370-1972

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✦ Synopsis

The low-temperature electrical conductivity sT of uncompensated insulating Si:P with P concentration N just below the metal±insulator transition (MIT), i.e. 3X0 Â 10 18 cm À3 $ N $ 3X5 Â 10 18 cm À3 , was measured between 0.05 and 5 K. With decreasing N, sT shows a crossover from Mott variable-range hopping (VRH) to Efros-Shklovskii VRH. The data on the insulating side can be described by the universal phenomenological scaling function proposed by Aharony et al. From the N dependence of the Mott temperature T M a correlation-length exponent n 1X1 is obtained, compatible with the conductivity exponent m % 1X3 for metallic samples. Indeed, the data on both sides of the MIT can be combined to yield dynamic scaling of sNY T. Upon lowering N on the insulating side further, a change from Efros-Shklovskii VRH to simple activated conduction is observed near N % 2X7 Â 10 18 cm À3 . This is attributed to the activation from the lower to the upper Hubbard band, as inferred from a sign change in the thermoelectric power and the absence of such a feature in compensated Si:(P, B).

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