1/f noise in delta-doped GaAs analyzed in terms of mobility fluctuations

This paper presents 1/f noise measurements on Si delta-doped GaAs structures. The samples are characterized by Hall, magnetoresistance, and Schubnikov-de Haas measurements. The distribution of electrons over the two lowest subbands in these structures varies with temperature and illumination, and so does the noise. The 1/f noise is characterized by the usual parameter alpha. We show in detail how to interpret the 1/f noise in the two-subbands system. We find that alpha increases by a factor of 30 upon population of a second subband either by illuminating the sample or by raising the temperature to 100 K. This strong increase in the 1/f noise is successfully described by the mobility fluctuation model, where only the lattice scattering contributes to the 1/f noise. The 1/f noise of the electrons in both subbands can be characterized by the same value of alpha(L)=0.4, which is strong support for the model.