Abstract
Persistent high-frequency (hf) hopping conductivity near the middles of well developed quantum Hall plateaus has been studied in the Si modulated heterostructures GaAs/Al0.3Ga0.7As, both δ- and modulation doped, under successive infrared irradiation in the 0.8 - 1.44 micron region. The conductivity has been determined by simultaneous measurement of attenuation and velocity of surface acoustic waves. With the increase of the radiation dose the conductivity decreases, whereas the carrier density in the 2D channel grows. There is a threshold of the persistent conductivity from the low energy side located between 0.86 and 0.48 eV. The observed behavior can be attributed to the so-called DX - centers which are localized two-electron states bounded by local lattice distortion. Such states, as known, exist in Si-doped GaAs/AlxGa1-xAs with x ≈ 0.3. We believe that hf hopping is due to tunneling of electron pairs between a two-electron center and its empty neighbor.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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