Forums

photodiode voltage

Started by Unknown June 8, 2020
https://optodiode.com/pdf/SXUV5DS.pdf

That's a common trick in the exotic photodiode biz.

The part has guaranteed 5 volt reverse. Typ breakdown is 20. It's
tested for speed at 15. The graphs go to 25.

What's a boy to do?

I did one EUV diode preamp (not this diode) where I allowed the system
to program bias up to -75 volts. The customer made me limit the
voltage to -10, by means of a password (in an FPGA!) that they
insisted I not reveal to them.



-- 

John Larkin         Highland Technology, Inc

Science teaches us to doubt.

  Claude Bernard
  
On Monday, June 8, 2020 at 11:52:00 AM UTC-4, jla...@highlandsniptechnology.com wrote:
> https://optodiode.com/pdf/SXUV5DS.pdf > > That's a common trick in the exotic photodiode biz. > > The part has guaranteed 5 volt reverse. Typ breakdown is 20. It's > tested for speed at 15. The graphs go to 25. > > What's a boy to do?
Find another diode? Call them and ask what the spec means? The response goes to 1 nm! That's like an X-ray, I think. George H.
> > I did one EUV diode preamp (not this diode) where I allowed the system > to program bias up to -75 volts. The customer made me limit the > voltage to -10, by means of a password (in an FPGA!) that they > insisted I not reveal to them. > > > > -- > > John Larkin Highland Technology, Inc > > Science teaches us to doubt. > > Claude Bernard
On Mon, 8 Jun 2020 09:04:52 -0700 (PDT), George Herold
<ggherold@gmail.com> wrote:

>On Monday, June 8, 2020 at 11:52:00 AM UTC-4, jla...@highlandsniptechnology.com wrote: >> https://optodiode.com/pdf/SXUV5DS.pdf >> >> That's a common trick in the exotic photodiode biz. >> >> The part has guaranteed 5 volt reverse. Typ breakdown is 20. It's >> tested for speed at 15. The graphs go to 25. >> >> What's a boy to do? >Find another diode? Call them and ask what the spec means?
That might be a starting point. The data sheet makes no sense. The Hamamatsu uv photodiode that I've used has similar contradictory voltage specs. It seems to be a tradition. The killer is the c-v curve. I don't want to run these things at 5 volts.
> >The response goes to 1 nm! That's like an X-ray, I think.
And it's rising, off the graph! -- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
On Monday, June 8, 2020 at 12:43:44 PM UTC-4, jla...@highlandsniptechnology.com wrote:
> On Mon, 8 Jun 2020 09:04:52 -0700 (PDT), George Herold > <ggherold@gmail.com> wrote: > > >On Monday, June 8, 2020 at 11:52:00 AM UTC-4, jla...@highlandsniptechnology.com wrote: > >> https://optodiode.com/pdf/SXUV5DS.pdf > >> > >> That's a common trick in the exotic photodiode biz. > >> > >> The part has guaranteed 5 volt reverse. Typ breakdown is 20. It's > >> tested for speed at 15. The graphs go to 25. > >> > >> What's a boy to do? > >Find another diode? Call them and ask what the spec means? > > That might be a starting point. The data sheet makes no sense. > > The Hamamatsu uv photodiode that I've used has similar contradictory > voltage specs. It seems to be a tradition. The killer is the c-v > curve. I don't want to run these things at 5 volts.
Maybe it's over the whole temperature range? Perhaps 'our' Russian x-ray PD guy (I've forgotten his name...) will know.
> > > > >The response goes to 1 nm! That's like an X-ray, I think. > > And it's rising, off the graph!
Yeah... IDK what the x-ray absorption mechanism is.... just blasting electrons out of their orbitals at a guess. I wonder if the peak at ~15 nm is some deep electron state in Si? (The inner most electron should bind with an energy proportional to Z (Z is the nuclear charge) Si is Z=14 , 14*13eV ~ 180 eV ~7 nm. (13 eV is the rydberg.. hydrogen binding energy) George H.
> > > > > -- > > John Larkin Highland Technology, Inc > > Science teaches us to doubt. > > Claude Bernard
George Herold wrote:


> Yeah... IDK what the x-ray absorption mechanism is.... > just blasting electrons out of their orbitals at a guess.
Yes, of course. The graph is possibly misleading. As the energy goes up (wavelength goes down) the probability of an interaction (efficiency) goes down, but the number of charge carriers produced goes up. So, it actually gets LESS sensitive, statistically, but the output pulse will be bigger. Lots of people use Silicon detectors to detect X-rays (the modern digital medical/dental X-ray systems, for instance) and charged particles (nuclear physics). Lower energy photons and particles are stopped in the Si, higher energy ones deposit some energy there and punch through. Jon
On Mon, 08 Jun 2020 22:28:58 -0500, Jon Elson <elson@pico-systems.com>
wrote:

>George Herold wrote: > > >> Yeah... IDK what the x-ray absorption mechanism is.... >> just blasting electrons out of their orbitals at a guess. >Yes, of course. The graph is possibly misleading. As the energy goes up >(wavelength goes down) the probability of an interaction (efficiency) goes >down, but the number of charge carriers produced goes up. So, it actually >gets LESS sensitive, statistically, but the output pulse will be bigger.
The graph is amps per watt, and the energy per photon covers a 1000:1 range, so the 1 nm photons are relatively infrequent at a given power, but sure pack a punch.
> >Lots of people use Silicon detectors to detect X-rays (the modern digital >medical/dental X-ray systems, for instance) and charged particles (nuclear >physics). Lower energy photons and particles are stopped in the Si, higher >energy ones deposit some energy there and punch through. > >Jon
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On 2020-06-08 11:51, jlarkin@highlandsniptechnology.com wrote:
> > https://optodiode.com/pdf/SXUV5DS.pdf > > That's a common trick in the exotic photodiode biz. > > The part has guaranteed 5 volt reverse. Typ breakdown is 20. It's > tested for speed at 15. The graphs go to 25. > > What's a boy to do? > > I did one EUV diode preamp (not this diode) where I allowed the system > to program bias up to -75 volts. The customer made me limit the > voltage to -10, by means of a password (in an FPGA!) that they > insisted I not reveal to them.
'Breakdown' means different things in photodiode datasheets. For MPPCs/SiPMs, the 'breakdown voltage' is sort of like the Early voltage for a BJT: it's defined as the point where the extrapolated gain vs. bias voltage line predicts a gain of 1.0, and you're expected to run the device a few volts above there. That datasheet arbitrarily defines 'breakdown' as the voltage where the reverse leakage is 1 uA, but doesn't quote an abs max voltage. The leakage rises very gently with bias, so the avalanche voltage is obviously quite a bit above the 25V range of the graphs. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
On Wed, 10 Jun 2020 08:58:43 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>On 2020-06-08 11:51, jlarkin@highlandsniptechnology.com wrote: >> >> https://optodiode.com/pdf/SXUV5DS.pdf >> >> That's a common trick in the exotic photodiode biz. >> >> The part has guaranteed 5 volt reverse. Typ breakdown is 20. It's >> tested for speed at 15. The graphs go to 25. >> >> What's a boy to do? >> >> I did one EUV diode preamp (not this diode) where I allowed the system >> to program bias up to -75 volts. The customer made me limit the >> voltage to -10, by means of a password (in an FPGA!) that they >> insisted I not reveal to them. > >'Breakdown' means different things in photodiode datasheets. For >MPPCs/SiPMs, the 'breakdown voltage' is sort of like the Early voltage >for a BJT: it's defined as the point where the extrapolated gain vs. >bias voltage line predicts a gain of 1.0, and you're expected to run the >device a few volts above there. > >That datasheet arbitrarily defines 'breakdown' as the voltage where the >reverse leakage is 1 uA, but doesn't quote an abs max voltage. The >leakage rises very gently with bias, so the avalanche voltage is >obviously quite a bit above the 25V range of the graphs. > >Cheers > >Phil Hobbs
I wouldn't mind running that one at maybe 20 volts (I have 24 handy) to keep the speed up, but my customer wouldn't let me. The data sheet could have recommended operating conditions, but they usually don't. Leakage doesn't bother me because we can AC-couple and capture short bright light pulses, and auto-zero between pulses when we know it's dark. -- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
 
> I wonder if the peak at ~15 nm is some deep electron state in > Si? >
This is not a 15 nm transmission peak, but the absorption peak (edge 100 eV) of a thin "dead" insensitive layer of the detector.
On Wednesday, June 10, 2020 at 10:24:14 AM UTC-4, plastco...@gmail.com wrote:
> > I wonder if the peak at ~15 nm is some deep electron state in > > Si? > > > This is not a 15 nm transmission peak, but the absorption peak (edge 100 eV) of a thin "dead" insensitive layer of the detector.
Huh, OK thanks. I guess one needs to know the expected background rate to know if it's (the spectral feature) a bump or a dip. George H.