SPICE photodiode model--how to put in reverse transit time?

Question

Hi, all,

A Merry Christmas, first of all.

Now that the important stuff is out of the way, I've been thinking about photodiode models.

Photodiode speed is a fairly strong function of reverse bias, and many types of PIN PDs speed up amazingly when you crank up the bias that last little bit (often above the datasheet V_B) to fully deplete the bulk.

Other types are dominated by diffusion in the epi layer, which is too highly doped to be depleted before the device turns to lava.

The diffusion-dominated rise time goes quadratically with diameter, just like the RC rise time, but is typically slower, at least in red-enhanced devices with thick I layers.

The SPICE diode model doesn't seem to include a reverse transit time. Any suggestions of how to model reverse transit time effects in photodiodes?

Thanks

Phil Hobbs

Jim Thompson · Accepted Answer

miso · Answer

Phil Hobbs · Answer

Thanks, that's both interesting and digestible.  (Important feature on  Boxing Day.) ;) I'll have a whack at seeing whether the large-signal reverse recovery  accurately predicts the photodiode behaviour, which ideally should be on  the low-level injection end of the curve. The photocarriers are generated throughout the depletion zone at a low  rate, which is pretty different from the reverse recovery of an 1N4007. Cheers Phil Hobbs --  Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 USA +1 845 480 2058 hobbs at electrooptical dot net

SPICE photodiode model--how to put in reverse transit time?

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