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The conductivity, the Hall effect, and the noise of ion-implanted resistors is measured between 77 and 300 K. The temperature dependence of the carrier concentration in these boron-doped layers cannot be explained by the freeze-out of the boron acceptor level. Possible explanations are a temperature-dependent Hall factor r and a distribution of trap levels 0.1–0.2 eV above the valence-band edge. The mobility μ can be determined from the conductivity and the Hall-effect data. The mobility shows the highest value after annealing at 750 °C. The value of the 1/f noise parameter α shows a weak temperature dependence after annealing at 450, 550, 650, and 900 °C. After annealing at 750 °C the α value decreases from 10−5 at 300 K to lower than 2×10−7 at 77 K. The highest mobility μ gives the lowest 1/f noise parameter α. This indicates that more defects and lattice damage give more 1/f noise. Additional scattering mechanisms have much more influence on the 1/f noise parameter α than on the mobility μ.

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In a semiconductor the density of carriers in each subband fluctuates owing to intraband transitions. We consider the spectral density for number fluctuations and for conductance fluctuations arising from such intraband transitions. It is shown that the spectral density for number fluctuations equals zero. If the mobility is the same in all subbands, the spectral density for conductance fluctuations equals zero. Otherwise the conductance fluctuations show a non-1/ f spectrum.