Measurements of non-Gaussian noise in quantum wells

Gaussian generation-recombination is accepted to be a dominant mechanism of current noise source 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 likely originates 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 a 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 multiwell system is dominated by fluctuations of a single well, while in the n -type the noise appears as a superposition of many fluctuators associated with individual wells.