Hi, all, Most of the time I just model photodiodes as current sources with parallel capacitances, and put in any deviations by hand afterwards. At the moment I have an application where I need to do rather better than that, to explore the tradeoff between speed, bias voltage, and quantum efficiency. (It may wind up with custom photodiodes.) The only thing I've found in the free literature is a strange paper from some Serbian guys who use, like, 100 subcircuits to model one photodiode. I'm sure it would be good for my soul to do an approximate analytic solution of carrier transport as a function of device geometry and stick that in as a behavioural model, but at the moment I'm too busy and too lazy. Does anybody have a reference to a photodiode model that includes transit time, high level injection, and bias dependence? Thanks 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 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
SPICE model for photodiodes including transit time effects?
Started by ●May 15, 2012
Reply by ●May 15, 20122012-05-15
Phil Hobbs wrote:> Hi, all, > > Most of the time I just model photodiodes as current sources with > parallel capacitances, and put in any deviations by hand afterwards. At > the moment I have an application where I need to do rather better than > that, to explore the tradeoff between speed, bias voltage, and quantum > efficiency. (It may wind up with custom photodiodes.) > > The only thing I've found in the free literature is a strange paper from > some Serbian guys who use, like, 100 subcircuits to model one > photodiode. >The Eurocon paper from Lasovic et al? That almost had me clobbered once, but then again I am not exactly the big whizbang math genius.> I'm sure it would be good for my soul to do an approximate analytic > solution of carrier transport as a function of device geometry and stick > that in as a behavioural model, but at the moment I'm too busy and too > lazy. > > Does anybody have a reference to a photodiode model that includes > transit time, high level injection, and bias dependence? >Not all of that but maybe this helps in the search: http://www.nsti.org/publications/MSM/2001/pdf/302.pdf http://lib.semi.ac.cn:8080/tsh/dzzy/wsqk/spie/vol6621/66211e.pdf http://spie.org/x648.html?product_id=790834 L. Ravezzi, G. F. Dalla Betta, D. Stoppa, A. Simoni, "A versatile photodiode SPICE model for optical microsystem simulation" in MICROELECTRONICS JOURNAL, v. 31, n. 4 (2000), p. 277-282 -- Regards, Joerg http://www.analogconsultants.com/
Reply by ●May 15, 20122012-05-15
On Tue, 15 May 2012 10:21:06 -0400, Phil Hobbs wrote:> Hi, all, > > Most of the time I just model photodiodes as current sources with > parallel capacitances, and put in any deviations by hand afterwards. At > the moment I have an application where I need to do rather better than > that, to explore the tradeoff between speed, bias voltage, and quantum > efficiency. (It may wind up with custom photodiodes.) > > The only thing I've found in the free literature is a strange paper from > some Serbian guys who use, like, 100 subcircuits to model one > photodiode. > > I'm sure it would be good for my soul to do an approximate analytic > solution of carrier transport as a function of device geometry and stick > that in as a behavioural model, but at the moment I'm too busy and too > lazy. > > Does anybody have a reference to a photodiode model that includes > transit time, high level injection, and bias dependence?The go-to guy for photoelectric stuff on this group is a guy name Phil Hobbs; he seems to -- oh, wait. (Sorry -- couldn't resist) -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com
Reply by ●May 15, 20122012-05-15
Tim Wescott wrote:> > On Tue, 15 May 2012 10:21:06 -0400, Phil Hobbs wrote: > > > Hi, all, > > > > Most of the time I just model photodiodes as current sources with > > parallel capacitances, and put in any deviations by hand afterwards. At > > the moment I have an application where I need to do rather better than > > that, to explore the tradeoff between speed, bias voltage, and quantum > > efficiency. (It may wind up with custom photodiodes.) > > > > The only thing I've found in the free literature is a strange paper from > > some Serbian guys who use, like, 100 subcircuits to model one > > photodiode. > > > > I'm sure it would be good for my soul to do an approximate analytic > > solution of carrier transport as a function of device geometry and stick > > that in as a behavioural model, but at the moment I'm too busy and too > > lazy. > > > > Does anybody have a reference to a photodiode model that includes > > transit time, high level injection, and bias dependence? > > The go-to guy for photoelectric stuff on this group is a guy name Phil > Hobbs; he seems to -- oh, wait. > > (Sorry -- couldn't resist)Laziness has been a bit of a hobby of mine for awhile now. ;) 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 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●May 15, 20122012-05-15
On Tue, 15 May 2012 11:37:07 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>Tim Wescott wrote: >> >> On Tue, 15 May 2012 10:21:06 -0400, Phil Hobbs wrote: >> >> > Hi, all, >> > >> > Most of the time I just model photodiodes as current sources with >> > parallel capacitances, and put in any deviations by hand afterwards. At >> > the moment I have an application where I need to do rather better than >> > that, to explore the tradeoff between speed, bias voltage, and quantum >> > efficiency. (It may wind up with custom photodiodes.) >> > >> > The only thing I've found in the free literature is a strange paper from >> > some Serbian guys who use, like, 100 subcircuits to model one >> > photodiode. >> > >> > I'm sure it would be good for my soul to do an approximate analytic >> > solution of carrier transport as a function of device geometry and stick >> > that in as a behavioural model, but at the moment I'm too busy and too >> > lazy. >> > >> > Does anybody have a reference to a photodiode model that includes >> > transit time, high level injection, and bias dependence? >> >> The go-to guy for photoelectric stuff on this group is a guy name Phil >> Hobbs; he seems to -- oh, wait. >> >> (Sorry -- couldn't resist) > >Laziness has been a bit of a hobby of mine for awhile now. ;) > >Cheers > >Phil Hobbs"Laziness is the mother of invention." -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Reply by ●May 15, 20122012-05-15
Joerg wrote:> > Phil Hobbs wrote: > > Hi, all, > > > > Most of the time I just model photodiodes as current sources with > > parallel capacitances, and put in any deviations by hand afterwards. At > > the moment I have an application where I need to do rather better than > > that, to explore the tradeoff between speed, bias voltage, and quantum > > efficiency. (It may wind up with custom photodiodes.) > > > > The only thing I've found in the free literature is a strange paper from > > some Serbian guys who use, like, 100 subcircuits to model one > > photodiode. > > > > The Eurocon paper from Lasovic et al? That almost had me clobbered once, > but then again I am not exactly the big whizbang math genius. > > > I'm sure it would be good for my soul to do an approximate analytic > > solution of carrier transport as a function of device geometry and stick > > that in as a behavioural model, but at the moment I'm too busy and too > > lazy. > > > > Does anybody have a reference to a photodiode model that includes > > transit time, high level injection, and bias dependence? > > > > Not all of that but maybe this helps in the search: > > http://www.nsti.org/publications/MSM/2001/pdf/302.pdfThanks. That's sort of what I'm doing now, except that the model I'm using includes shot noise. Their data table doesn't make a lot of sense--they've got the device capacitances listed backwards, for one thing, but even so, the n+/p sub device is still too slow.> http://lib.semi.ac.cn:8080/tsh/dzzy/wsqk/spie/vol6621/66211e.pdf > http://spie.org/x648.html?product_id=790834 > > L. Ravezzi, G. F. Dalla Betta, D. Stoppa, A. Simoni, "A versatile > photodiode SPICE model for optical microsystem simulation" in > MICROELECTRONICS JOURNAL, v. 31, n. 4 (2000), p. 277-282Those all seem to be RC models decorated with various things like noise sources and lead inductance, which is the sort of thing I'm doing now. The reason I care is that larger photodiodes have different behaviour for photocurrent generated in different places. For obvious reasons they can't have a nice thick metal layer over top of the epi like ordinary diodes. The epi is heavily doped to improve its conductivity, so there's not much E field inside it, and the electrons have to travel mostly by diffusion. Heavy doping also reduces the carrier mobility. That tends to make regions of the diode far from the contact slow down quadratically with increasing diameter, which is something I care about a lot. The quadratic slowdown is masked in datasheet curves, because the RC delay is going quadratically with diameter as well. However, the RC delay is position-independent, so there's a big difference in performance for things like noise cancellers, which rely on the photocurrent being a faithful replica of the incident beam power no matter where it happens to land. There are Schottky-barrier photodiodes and double Schottky barrier (interdigitated) photodiodes, which have metal top layers, but not in any decent sizes like 1-3 mm diameter. Some clever sub-wavelength interdigitated structure could probably be nearly independent of position and polarization, but now is not the time to launch a research project on photodiode design, though it might be fun eventually. 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 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●May 15, 20122012-05-15
John Larkin wrote:> > On Tue, 15 May 2012 11:37:07 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > > >Tim Wescott wrote: > >> > >> On Tue, 15 May 2012 10:21:06 -0400, Phil Hobbs wrote: > >> > >> > Hi, all, > >> > > >> > Most of the time I just model photodiodes as current sources with > >> > parallel capacitances, and put in any deviations by hand afterwards. At > >> > the moment I have an application where I need to do rather better than > >> > that, to explore the tradeoff between speed, bias voltage, and quantum > >> > efficiency. (It may wind up with custom photodiodes.) > >> > > >> > The only thing I've found in the free literature is a strange paper from > >> > some Serbian guys who use, like, 100 subcircuits to model one > >> > photodiode. > >> > > >> > I'm sure it would be good for my soul to do an approximate analytic > >> > solution of carrier transport as a function of device geometry and stick > >> > that in as a behavioural model, but at the moment I'm too busy and too > >> > lazy. > >> > > >> > Does anybody have a reference to a photodiode model that includes > >> > transit time, high level injection, and bias dependence? > >> > >> The go-to guy for photoelectric stuff on this group is a guy name Phil > >> Hobbs; he seems to -- oh, wait. > >> > >> (Sorry -- couldn't resist) > > > >Laziness has been a bit of a hobby of mine for awhile now. ;) > > > >Cheers > > > >Phil Hobbs > > "Laziness is the mother of invention."Or the father, as my mum used to say. (Of course she may have been biased.) ;) 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 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●May 15, 20122012-05-15
On Tue, 15 May 2012 11:37:07 -0400, Phil Hobbs wrote:> Tim Wescott wrote: >> >> On Tue, 15 May 2012 10:21:06 -0400, Phil Hobbs wrote: >> >> > Hi, all, >> > >> > Most of the time I just model photodiodes as current sources with >> > parallel capacitances, and put in any deviations by hand afterwards. >> > At the moment I have an application where I need to do rather better >> > than that, to explore the tradeoff between speed, bias voltage, and >> > quantum efficiency. (It may wind up with custom photodiodes.) >> > >> > The only thing I've found in the free literature is a strange paper >> > from some Serbian guys who use, like, 100 subcircuits to model one >> > photodiode. >> > >> > I'm sure it would be good for my soul to do an approximate analytic >> > solution of carrier transport as a function of device geometry and >> > stick that in as a behavioural model, but at the moment I'm too busy >> > and too lazy. >> > >> > Does anybody have a reference to a photodiode model that includes >> > transit time, high level injection, and bias dependence? >> >> The go-to guy for photoelectric stuff on this group is a guy name Phil >> Hobbs; he seems to -- oh, wait. >> >> (Sorry -- couldn't resist) > > Laziness has been a bit of a hobby of mine for awhile now. ;)If I were any better at device-level modeling I'd offer myself as a resource to do the work. As it is I think I could do a dynamite job if it was in LTSpice and if you had a white paper that spelled out the effects, which you just needed to be translated into SPICE-ese. But only given those two conditions: even if you had the clear and concise paper but not LTSpice, I'd have to decline. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
Reply by ●May 15, 20122012-05-15
Tim Wescott wrote:> > On Tue, 15 May 2012 11:37:07 -0400, Phil Hobbs wrote: > > > Tim Wescott wrote: > >> > >> On Tue, 15 May 2012 10:21:06 -0400, Phil Hobbs wrote: > >> > >> > Hi, all, > >> > > >> > Most of the time I just model photodiodes as current sources with > >> > parallel capacitances, and put in any deviations by hand afterwards. > >> > At the moment I have an application where I need to do rather better > >> > than that, to explore the tradeoff between speed, bias voltage, and > >> > quantum efficiency. (It may wind up with custom photodiodes.) > >> > > >> > The only thing I've found in the free literature is a strange paper > >> > from some Serbian guys who use, like, 100 subcircuits to model one > >> > photodiode. > >> > > >> > I'm sure it would be good for my soul to do an approximate analytic > >> > solution of carrier transport as a function of device geometry and > >> > stick that in as a behavioural model, but at the moment I'm too busy > >> > and too lazy. > >> > > >> > Does anybody have a reference to a photodiode model that includes > >> > transit time, high level injection, and bias dependence? > >> > >> The go-to guy for photoelectric stuff on this group is a guy name Phil > >> Hobbs; he seems to -- oh, wait. > >> > >> (Sorry -- couldn't resist) > > > > Laziness has been a bit of a hobby of mine for awhile now. ;) > > If I were any better at device-level modeling I'd offer myself as a > resource to do the work. As it is I think I could do a dynamite job if > it was in LTSpice and if you had a white paper that spelled out the > effects, which you just needed to be translated into SPICE-ese. > > But only given those two conditions: even if you had the clear and > concise paper but not LTSpice, I'd have to decline.Thanks! I'm using LTspice, but haven't found the clear and concise paper yet. :( Cheers Phil -- 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 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●May 15, 20122012-05-15
Phil Hobbs wrote: [...]> The reason I care is that larger photodiodes have different behaviour > for photocurrent generated in different places. For obvious reasons > they can't have a nice thick metal layer over top of the epi like > ordinary diodes. The epi is heavily doped to improve its conductivity, > so there's not much E field inside it, and the electrons have to travel > mostly by diffusion. Heavy doping also reduces the carrier mobility. > > That tends to make regions of the diode far from the contact slow down > quadratically with increasing diameter, which is something I care about > a lot. The quadratic slowdown is masked in datasheet curves, because > the RC delay is going quadratically with diameter as well. However, the > RC delay is position-independent, so there's a big difference in > performance for things like noise cancellers, which rely on the > photocurrent being a faithful replica of the incident beam power no > matter where it happens to land. >It also lowers the average speed so it's probably not just a concern to engineers trying to cancel noise.> There are Schottky-barrier photodiodes and double Schottky barrier > (interdigitated) photodiodes, which have metal top layers, but not in > any decent sizes like 1-3 mm diameter. Some clever sub-wavelength > interdigitated structure could probably be nearly independent of > position and polarization, but now is not the time to launch a research > project on photodiode design, though it might be fun eventually. >A group of scientists from Japan had that patented and I wouldn't be surprised if some company started making them. Usually they are called interdigital electrodes. ... oh, this might be it: http://jp.hamamatsu.com/products/light-source/1008/pd383/index_en.html -- Regards, Joerg http://www.analogconsultants.com/
