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HL: Halbleiterphysik

HL 12: Poster I: Quanten Hall Effekt (1-9), II-VI Halbleiter (10-17), Epitaxie (18-23), Quantenpunkte und -dr
ähte (24-50), Photonik (51-59), Metall-Isolator Übergang (60-64), Si/Ge (65-67), Elektronentheorie (68-69), Amorphe Halbleiter, Ionen-Implantation

HL 12.4: Poster

Montag, 27. März 2000, 14:00–19:00, A

High Frequency Conductivity in the Quantum Hall Effect — •F. Hohls¹, U. Zeitler¹, R. J. Haug¹, and K. Pierz² — ¹Inst. f. Festkörperphysik, Uni Hannover — ²PTB, Braunschweig

We have measured the ac-conductivity of a two dimensional electron

system (2DES) at the transition between integer quantum Hall

plateaus for frequencies from 100 kHz to 6 GHz. In addition we

measured the temperature dependence between 50 to 700 mK.

The 2DES is realized by a standard GaAs/AlGaAs heterostructure

and patterned into Corbino geometry.

The measured Shubnikov-de Haas (SdH) peaks

are analyzed for filling factors up to six. We show an analysis of

peak width and height and compare the frequency effects with the

temperature dependence.

We observe a dramatic increase of the peak value for frequencies

between 1 MHz and 1 GHz. While at low frequencies all SdH peaks

at different filling factors

show different values of conductivity (0.02 - 0.05 e²/h),

they converge at frequencies above 2 GHz to the same value of

0.17 e²/h. This value is three times smaller than the

theoretical predicted universal value of 0.5 e²/h. We

do not observe a similar converging peak value as function

of temperature though 700 mK compares to a photon energy of

15 GHz.