What is the temperature dependence of the NIRCam sensor's responsivity?

[Devin-M]

In this one, the dark current decreases as the forward bias voltage increases above 0v:

Fig. 2. Dark current-bias characteristics of the MWIR MCT detector at (a) 77 K

https://opg.optica.org/oe/fulltext.cfm?uri=oe-28-16-23660&id=433783

 

[collinsmark]

In this one, the dark current decreases as the forward bias voltage increases above 0v:

[...]

https://opg.optica.org/oe/fulltext.cfm?uri=oe-28-16-23660&id=433783

C'mon, @Devin-M. Please. The paper discusses the discrepancies in the text and addresses some of the problems such as the imperfection of the cold shield. I mean, it's right there.

You've been repeating a lot of similar figures. Possible non-ideal behaviors and measurement errors have already been addressed several posts back by myself and others.

I'm tempted to repeat some of those points on the subject. Can you guess which points I'm tempted to repeat?

 

[Devin-M]

This one shows the same effect… at 110k, the dark current decreases as the bias voltage increases just above 0v…

http://wrap.warwick.ac.uk/114498/1/...thically-integrated-silicon-Beanland-2019.pdf

 

[Grinkle]

at 110k, the dark current decreases as the bias voltage increases just above 0v…

How do you interpret this data (what do you think it implies)?

For myself, the first thing I would check is pixelation, I'd ask the presenter if they could show the table of raw data to make sure its not just that (pixelation). Its a little hard to say for sure, but I think the 180K line is showing the same thing, and to my eye, one can't tell about the other temp lines, because they all overlap too much around 0V bias.

 

[Devin-M]

Fig 4A shows the dark current density at 77k, Fig 4C shows the photocurrent at 77k when illuminated by a 5mW laser… both show decreasing current with increasing bias voltage between 0.0v and 0.1v…

https://www.nature.com/articles/s41377-020-00453-x.pdf

 

[collinsmark]

@Devin-M, let me point out something else that you may be running into besides measurement errors and non-deal aspects of circuit setups.

The emf point at which a photodetector exhibits zero [dark] current is not necessarily at exactly 0 Volts. It's highly dependent upon the circuit in which it is placed. This is due to the fact that photodetectors are non-linear devices and have junction emfs. The P-doped and N-doped material in the photodetectors act as dissimilar metals (or in this case, dissimilar semiconductors) and a residual emf maybe present across its terminals, even though no current flows.

Certainly, if the photodetector is by itself, not connected to anything, this emf will exist. It can also exist if placed in a circuit, particularly when other non-linear devices, such as a diode, are wired in parallel.

As an analogy, this is similar to how you wire two batteries in parallel, and no current will flow between them. Don't take this analogy too far though -- batteries have significant energy stored within them, but diodes do not. (And photodetectors do not contain significant stored energy when they and their sourroundings are all at the same temperature.)

So the idea that the voltage across the terminals of a photodetector is not precisely 0 when the minimum current point is reached, should not come as a complete surprise. Again though, it all depends on the circuit details.

-------------------

But let me repeat my main point again. If you place a photodetector in a passive circuit, and the photodetector, the other circuit components, and the surroundings are all at the same temperature (that also means no external light sources -- only the thermal background within the dark enclosure), the current through the photodetector will be zero. A this point, the voltage across the terminals of the photodetector might not be exactly 0, but I can guarantee you that the steady-state, DC current through the photodetector will be 0.

 

[Grinkle]

@Devin-M To circle back on post #64, your post #65 is clearly not pixelation around the zero point, my question is answered on that.

 

[Devin-M]

Fig 5(a) shows that exposure to laser light can shift the knee of the graph further away from 0.0v bias voltage into the positive bias voltage territory…

http://cpb.iphy.ac.cn/article/2019/2015/cpb_28_12_128501.html

 

[Grinkle]

@Devin-M You might this (Physics of Laser Based Failure Analysis) interesting.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjO9uWZ4bL5AhVVj2oFHcj0D3UQFnoECAIQAQ&url=http://sites.bu.edu/bifano/files/2018/03/vigil_2014.pdf&usg=AOvVaw2ibi7Da-tIQDQGHKjDFQ3u

 

[russ_watters]

View attachment 312635
https://apps.dtic.mil/sti/pdfs/ADA429637.pdf

Hi @Devin-M - please stop posting links and pictures with no discussion. This is a discussion forum, not a news aggregator. If you have anything productive to say, say it.

 

[Devin-M]

Sorry I was responding to this comment:

You can assume though that if the sensor was actually placed in a passive circuit, such that the photodetector, other components in the circuit, its enclosure, and everything else in the vicinity is all at the same temperature, the dark current density would measure 0.

I was wondering what powers the dark current measured in the paper when there is zero bias voltage, in the dark, and the sensor and surroundings at the same temperature? From Ohm's law we have P=I^2R

View attachment 312635
https://apps.dtic.mil/sti/pdfs/ADA429637.pdf