DX-centers and long-term effects in the high-frequency hopping conductance in Si-doped GaAs/Al0.3Ga0.7As heterostructures in the quantum Hall regime: acoustical studies

It is discovered that both high-frequency (hf) hopping conductance and electron density in the 2D channel, ns, in Si δ-doped and modulation-doped GaAs/Al0.3Ga0.7As heterostructures at the plateaus of the integer quantum Hall effect depend on cooling rate of the samples. Furthermore, consecutive IR illumination leads to a persistent hf hopping photoconductance, which decreases when the illumination intensity increases, while ns increases. The persistent hf hopping photoconductance occurs when the illumination frequency exceeds a threshold, which is between 0.48 and View the MathML source. The results are attributed to two-electron defects (so-called DX-centers) located in the Si-doped layer of the Al0.3Ga0.7As heterostructure.