General transport theory of noise in PN junction-like devices—II. Carrier correlations and fluctuations for high injection

Abstract A computation is given of the hole-density spatial correlation function in the N -region of a one dimensional P + N junction in the high-injection limit. Recombination processes which involve transitions through Shockley-Read levels with arbitrary capture ratio for electrons and holes (expressed by the parameter y = τ n 0 / τ p 0 ) are considered. Contrary to the low injection case or to high injection with quasi band-band recombination the covariance function shows a delta-function part which represents an approximation for correlations on a molecular scale, and a long-range part (for y ≠ 1) which persists over many diffusion lengths. This behaviour is in accord with general predictions for correlations in a non-equilibrium, non-homogeneous system. The density spectra are calculated next. Computer computations indicate smooth spectra for x = x ′, with a plateau for small ω and ω − 1 2 asymptote for large ω; the spectra for x ≠ x ′ oscillate between negative and positive values. Finally, these results are used to compute the derivative spectra and the junction current noise, and the low and high frequency behaviour is discussed. The asymmetry of the SR levels modifies the noise by as much as 33 per cent, but the general trends of the previous high injection results [1] are confirmed. I.e., for small ω there is a slight reduction in noise for P + N junctions, depending on b (mobility ratio), γ (hole current fraction) and y (SR parameter). For an N + P junction a noticeable enhancement is predicted.