Electrical fluctuations and the quantized Hall effect

Fluctuations in the Hall and Shubnikov-de Haas voltages were studied on a CaAs/Al x Ga 1- x As heterostructure operating in the integral quantized Hall regime. In the spectral noise intensities two contributions could be distinguished, i.e., a frequency and current independent contribution and a frequency and current dependent one. The first could be associated with velocity fluctuations of charge carriers (thermal noise). The second contribution is associated with carrier density fluctuations and could be interpreted in terms of generation-recombination noise due to transitions to and from localized states in the wings of the Landau levels.