Current noise in dielectrics and semiconductors is investigated under the following conditions: double injection, negligible traps and recombination centre effects, space-chargelimited region, negligible diffusion and direct ielectron-hole recombination. A method of calculating the spectral noise density based on the Lax approach and the Debye-Huckel position correlations between carrier densities is used. Expressions for low and high frequencies are given in closed form; an enhancement effect is found a t low frequencies. In the limit of the quasineutral (ambipolar) region, a small correction to the Hill-van Vliet formula is obtained.
IntrodlietionI n the presence of both electrons and holes, from the standpoint of current noise, we may distinguish two differeng situations : a ) Conduction without injection, when the electrical neutrality may be violated only by fluctuations. Under charge neutrality conditions, the noise problem was the object of detailed studit's concerning the effect of drift, diffusion, presence of traps and recombination centres etc. [l to 41.b) The double injection case, when the solid is no more neutral (even on an average), the current-voltage characteristic is non-linear, the carrier densities and the electrical field vary inside the sample. This case is more difficult; even the exact analytical solution of the stationary current problem is hard to obtain, and some approximations are necessary [5 to 91.In this paper we try to study the current noise of injected electrons and holes. \Ve take into consideration the direct (bimolecular) recombination and neglect traps, recombination centres, and diffusion effects in the same way as Parmcnter and Ruppel did for the stationary problem [8].The computational method consists in solving the differential equation obeyed by the spectral density distribution of the current noise. The space charge effects are introduced both by the presence of some corresponding terms in this equation and by accounting for the spatial correlations between carrier densities.25 phqsica 2Sjl