On the Hooge relation in semiconductors and metals

The expressions describing the low frequency noise caused by defects in semiconductors and metals have been obtained in the framework of a general unified approach for both fluctuations in the number of carriers and their mobility. When fluctuations in the number of carriers are responsible for noise, the spectral noise density is inversely proportional to the carrier concentration squared and to the volume of the sample. The spectral density of the noise caused by mobility fluctuations is inversely proportional to the sample volume, and does not depend either on carrier concentration or on the total number of carriers. In the case when both mechanisms contribute to noise and they are correlated, the dependence of the noise on the number of carriers depends on the relative contribution of these two noise mechanisms. The expressions obtained can be associated with corresponding cases of the 1/f noise. The physical basis and limitations of the Hooge formula are discussed. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3186620]