The effect of an electric-field gradient on avalanche noise

Abstract

The effect of an electric-field gradient on the excess avalanche noise is examined using both a Monte Carlo model and experiment. Nonlocal effects cause the noise to be significantly reduced as the electric-field gradient increases in a p+–n junction. For equal electron and hole ionization coefficients, lower noise is always achieved when carriers are injected into the high field end of these structures. Furthermore, for a constant noise figure and depletion thickness, a higher gain is always achieved in a p+–n junction compared a p+–i–n+. The results are explained in terms of coherence in ionization events.

Plasmonic field confinement for separate absorption-multiplication in InGaAs nanopillar avalanche photodiodes

“…A key assumption of their work was that (1) a carrier experiences a spatially uniform electric field and (2) the multiplication region is much larger than the ionization path length, such that the excess noise at a given gain, M , is determined by bulk ionization coefficients. However, since their early work it has been shown that shrinking the volume of the avalanche region 3 4 5 6 7 and engineering sharp gradients in the electric field 8 lowers the effective ratio of the ionization coefficients, , resulting in lower excess noise factors and higher gain-bandwidth products 9 10 beyond what is predicted by bulk values of the ionization coefficients. The improved statistics of the impact ionization process is attributed to the ionization path length of carriers having a narrower probability distribution due to dead space.…”

Low multiplication noise thin Al/sub 0.6/Ga/sub 0.4/As avalanche photodiodes

“…In our earlier work [19] we showed that in pn junctions with rapidly varying electric fields the noise is reduced further as the ionization events are localized in the vicinity of the peak field and thus the impact ionization process becomes even more deterministic. The present p-n diode shows low excess noise, similar to that produced by the p in diode with m, despite a much wider depletion width, for similar reasons.…”

Excess noise characteristics of single heterojunction AlxGa1-xAs-GaAs avalanche photodiodes

“…Despite its extreme simplicity this SMC model has proved capable of reproducing, at least qualitatively, many of the critical features of impact ionization and avalanche processes, including shapes of ionization path length pdf 34,36 , multiplication 34,36,37 , noise 34,36,37 , temporal behaviour 38,39 and temperature dependence of avalanche multiplication 40 .…”