Abstract-The effects of dead space (the minimum distance travelled by a carrier before acquiring enough energy to impact ionize) on the current impulse response and bandwidth of an avalanche multiplication process are obtained from a numerical model that maintains a constant carrier velocity but allows for a random distribution of impact ionization path lengths. The results show that the main mechanism responsible for the increase in response time with dead space is the increase in the number of carrier groups, which qualitatively describes the length of multiplication chains. When the dead space is negligible, the bandwidth follows the behavior predicted by Emmons but decreases as dead space increases.

No abstract

The time dependent current response to an impulse of injected carriers is calculated for an avalanche photodiode using Monte Carlo simulation. For low electric fields and long avalanche regions the results agree with the conventional model, which assumes that carriers travel always with their saturated drift velocities. However, while diffusion remains unimportant, for high fields and short avalanche regions, the conventional model underestimates the device speed. Monte Carlo simulations show that the mean downstream average velocity of ionizing carriers is significantly enhanced at high electric fields and agreement is restored if we allow for this effect in the conventional model.

Article:Hambleton, P.J., Ng, B.K., Plimmer, S.A. et al. (2 more ReuseUnless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request.

Numerical simulations predict that carriers which impact ionize shortly after their dead space travel to their ionization event with an average velocity much greater than their saturated drift velocity. The effect is argued to result from the fortuitously reduced phonon scattering which leads to this early ionization. Analytical models constructed using pictures of impact ionization similar to those of both Wolff and Shockley give good agreement with Monte Carlo simulations of the effect.