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Electric Low-Frequency Noise in Semiconductors


B.I. Yakubovich

Electric low-frequency noise in semiconductors was investigated. Electric low-frequency fluctuations in semiconductors are determined, as a rule, by excess noise which usually prevails over other types of noise in the field of low frequencies. Excess noise – the noise, which spectrum has the form S (f )~1/f α where α it is close to 1. Noise of this type is widely investigated, and its studying is important for the decision both fundamental, and technical problems. The purpose of this article – to give the quantitative description of electric low-frequency noise in semiconductors, and to establish connection of noise with characteristics of semiconductors. Excess low-frequency noise in semiconductors is considered. The noise arising owing to capture and emission of carriers of a charge by traps, the formed defects of structure is analysed. At first the spectrum of fluctuations of the current caused by one trap was determined. It is considered the rather general case fluctuation process when the probability of capture of the carrier on a trap is statistically connected with time its staying in a free state, and the probability of emission of the carrier is statistically connected with time carrier staying in the bound state on a trap, statistical connections are set in a general form. The spectrum of fluctuations in this case is calculated. The ratios connecting parametres fluctuation process with characteristics of the semiconductor are determined. The expression connecting spectral density of noise, caused by a trap, with semiconductor characteristics is as a result calculated. Further the noise spectrum in the semiconductor which is determined by set of traps available in it was calculated. As a result expression for a spectrum of excess low-frequency noise in semiconductors is obtained. The calculated expression describes a spectrum of electric low-frequency fluctuations in the semiconductors caused by traps in the rather general case: there are statistical connections between consecutive events of process of capture and emission of carriers by a trap, and statistical connections are set in a general form. The obtained expression is fair for onecharge traps formed by different types of defects of structure. It can be applied to semiconductors of various types. From the formula obtained in the article the kind of dependences of spectral density of low-frequency noise from the characteristics of the semiconductor influencing noise follows. Results of the theoretical analysis carried out in the article, are in good conformity with the data of numerous experimental researches. The obtained results can be applied to the analysis of spectra and a noise level estimation in semiconductor materials, for decrease in noise and improvement of characteristics of semiconductor devices, for fluctuation spectroscopy of semiconductors.

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