Conduction Mechanisms for Electronic Devices.
Final rept. on Phase 2, 3 May 72-2 May 73,
RCA LABS PRINCETON N J
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Detailed measurements of the electronic transport properties in controlled-occupancy energy band tails have revealed unexpected new results which have significant implications for the understanding of disordered semiconductors. Foremost is the finding that at low temperatures approximately 20 K the temperature dependence of the conductivity is accurately described by log sigma approximately equal to T to the -12 power, not T to the -14 power, as predicted by Mott and others. The only theory that does predict our result applies to one-dimensional, random, hopping conduction not three. Since this is the first extensive test of these theories at the necessary low temperatures, serious questions of theoretical interpretation are raised. It is suggested that these results may be attributed to the filamentary character of electronic conduction paths in random potentials. The previously observed exponential dependence of conductivity on electric field strength has been found to extend to as low as 2 Vcm at 4.2 K and to have a sensitivity which increases further at lower temperatures. Measurements of the thermoelectric power at 5 to 10 K and at 77 K give somewhat inconsistent results the 77 K data are in better agreement with expectations based on Fermi level shifts within the band tails. Author
- Solid State Physics