Berlin 2008 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 28: Transport properties

HL 28.1: Talk

Tuesday, February 26, 2008, 09:30–09:45, ER 164

Influence of electronic correlations on the frequency-dependent hopping transport in Si:P — •Elvira Ritz and Martin Dressel — 1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550, Stuttgart

At low energy scales charge transport in the insulating Si:P is by activated hopping between the localized donor electron states. Theoretical models for a disordered system with electron-electron interaction are appropriate to interpret the electric conductivity spectra [2]. With a novel and advanced method [3,4] we have measured the complex broadband microwave conductivity of Si:P from 0.1 to 5 GHz in a broad range of phosphorus concentration from 0.56 to 0.95 relative to the critical value n_c=3.5× 10¹⁸ cm⁻³ corresponding to the metal-insulator transition driven by doping. At T=1.1 K the samples show a super-linear frequency dependence of the conductivity indicating the influence of the Coulomb gap. At higher doping n→ n_c, an abrupt drop in the conductivity power law σ₁(ω)∼ω^α is observed. The dielectric function ε₁ increases upon doping following a power law in (1−n/n_c). Dynamic response at elevated temperatures is also discussed.

[1] E. Ritz and M. Dressel, arXiv:0711.1256, in print

[2] B. I. Shklovskii and A. L. Efros, Zh. Eksp. Teor. Fiz. 81, 406 (1981) [Sov. Phys. JETP 54, 218 (1981)]

[3] M. Scheffler and M. Dressel, Rev. Sci. Instrum. 76, 074702 (2005)

[4] E. Ritz and M. Dressel, to be published