Measurements of non-Gaussian noise in quantum wells

Gaussian generation-recombination is known to be a dominant mechanism of current noise in quantum well systems biased by electric field normal to the layers. We have found pronouncedly non-Gaussian excess current noise in n-type and p-type multiple quantum wells. The non-Gaussian noise has been attributed to metastable spatial configurations of electric field. The metastability is likely originating from negative differential conductance caused by intervalley scattering in n-type wells and heavy and light holes tunneling in p-type wells. At a constant bias the quantum well system randomly switches between a high resistivity state with low current flow and low resistive state with high current flow. The non-Gaussianity of the noise is more pronounced in p-type wells where the time traces of current fluctuations resemble closely two-level random telegraph signal which has not been straightforwardly observed in n-type wells. The non-Gaussian character of the noise in n-type systems has been revealed by measurements of nonzero skewness of the amplitude distributions. The difference between noise properties of n- and p-type systems has been attributed to small capture probability of electrons in n-type wells, as opposed to very high capture probability of holes in p-type wells. As a consequence the noise of any p-type multi-well system is dominated by fluctuations of a single while in the n-type the noise appears as a superposition of many fluctuators associated with individual wells.