Suppression of low-frequency noise in two-dimensional electron gas at   degenerately doped Si:P \delta-layers
  We report low-frequency 1/f noise measurements of degenerately doped Si:P \delta-layers at 4.2K. The noise was found to be over six orders of magnitude lower than that of bulk Si:P systems in the metallic regime and is one of the lowest values reported for doped semiconductors. The noise was found to be nearly independent of magnetic field at low fields, indicating negligible contribution from universal conductance fluctuations. Instead interaction of electrons with very few active structural two-level systems may explain the observed noise magnitude 
Saquib Shamim, Suddhasatta Mahapatra, Craig Polley, Michelle Y.   Simmons and Arindam Ghosh
cond-mat.mes-hall