CCDs, MOS and Single photon counting pixels

[Mishra]

Hello,
I need to learn as much as I can about single photon counting pixel detectors (producing a signal for each photons hitting the detector) e.g. PILATUS. I do not understand how this type of detectors counts single photons as opposed to integrating the energy of multiple photons (CCD, MOS, CMOS...). By which mechanism does one reach the single photon counting mode ?

Also, I understand that a CCD detector is basically an array of MOS capacitors. From what I understand of MOS, the gate voltage applied between the metal and the p-type silicon creates a depletion region. The photoelectrons produced in the depletion region will be trapped in it, while the hole will leave the region. My question is: is this depletion region used to trap the photoelectrons ? Is this depletion region considered as the potential well seen in this representation: http://tinyurl.com/lxlhcjq ?

If anyone has resources on these subjects I would be glad to read them,
thanks!

 

[eljose79]

Hello,

Thank you for your question about single photon counting pixel detectors. These types of detectors, such as PILATUS, are able to count individual photons because they are designed with a very high spatial resolution, meaning that each pixel is able to detect and count individual photons. This is achieved through a combination of advanced electronics and specialized materials.

One mechanism that allows these detectors to count single photons is through the use of avalanche photodiodes (APD). These are highly sensitive semiconductor devices that are able to amplify the signal from a single photon, allowing it to be detected and counted. APDs are often used in conjunction with a scintillator material, which converts the photon into a burst of light that can then be detected by the APD.

As for your question about CCD detectors, you are correct in understanding that they work by trapping photoelectrons in a depletion region created by a gate voltage. This depletion region acts as a potential well for the photoelectrons, allowing them to be detected and counted. The depletion region is not necessarily used to trap the photoelectrons, but rather to create an electrical potential that can be measured and counted.

I would recommend looking into resources on avalanche photodiodes and CCD detectors for more in-depth information on their mechanisms and capabilities. There are also many scientific papers and articles available online that discuss the use of these detectors in various applications.

I hope this helps answer your questions and provides some resources for further reading. Best of luck in your research!