Dear Quang Tran Van ,

Welcome!

The most appropriate radiation detector is the pin diode. Its dark current is low and it is quite sensitive to the the incident radiation. There are large area photo diodes that you can try using them as radiation detector.

If you want to increases the detectivity of the diode you can cool down to reduce it dark current.

You can also use chopper to distinguish the radiation from the dark current.

Best wishes

Do you mean Ionizing radiation, or RF radiation?

Your guess is appliable to RF, and there is no problem with noise.

But I guess, your guess is about ionizing RAD detectors.

So it is not necessarily a PN junction...

I mean, the final digitizer will take the PN signal, but the body is not a junction.

The ionizing radiation ionizes.

So you need either easily ionizable low thermal nose media, or cascade-style charge multiplying media/device, or both in one body.. or lay them one on top of another. That is how it works. Well.. basic consumer detectors are just big diodes, so you are right here.

You would like to have a metal/intrinsic semiconductor/metal structure. The semiconductor should be of high quality in order to possess a large product of charge carrier mobility and recombination lifetime (both parameters should be as large as possible). The intrinsic charge carrier concentration is determined as Ni = (NcNv)^0.5*exp(-Eg/2kT), were Nc and Nv are the effective density of states in the conduction and valance bands, respectively. As it becomes clear from the equation there two options to keep the thermal generation current (proportional to Ni) small. The first and most straightforward way is to cool down the detector.

Ideally to liquid nitrogen temperature, but more practical two- or three-stage thermoelectric cooling can also work quite well. The second option is to use a wide bandgap semiconductor Eg > 1.5 eV (most common are CdTe, CdZnTe). However, it may be very challenging to obtain a high-quality wide-bandgap intrinsic compound semiconductor. Thus, these samples are quite expensive. Some additional information can be found in my paper.

https://www.nature.com/articles/s41598-018-37637-w

Thin film CdZnTe, CdTe, HgI2, or BiI3 detectors are reported in the literature - especially for medical x-ray imaging.

The following paper may be interesting:

A sensitive and robust thin-film x-ray detector using 2D layered perovskite diodes, Science Advances  10 Apr 2020: Vol. 6, no. 15, eaay0815,

DOI: 10.1126/sciadv.aay0815

You have to specify. You might build a cheap semiconductor for alphas or X-rays. For detection of gammas you will usually need a relatively big crystal which is never cheap.

Most silicon particle detectors work, in principle, by doping narrow (usually around 100 micrometers wide) strips of silicon to turn them into diodes, which are then reverse biased. As charged particles pass through these strips, they cause small ionization currents that can be detected and measured.

Thank you very much for all your answers. It is greatly appreciated Artur Braun ; Andrey Porokhnyuk ; Viktor Brus ; Krishnan Raja ; Erik Strub ; Soad Mohialdin

I agree with Erik Strub, PhD - you must specify the specification of the radiation. If optical, see brief descriptions of my 2 patents on my account (on this topic): 1- Optical ADC radiation-digital code .. (UA139591 01.10.2020); 2- Method .... UA 142327 05.25.2020, etc.

Nick Proskurin, PhD.

No need to build it. Just get yourself a webcam. You can use a webcam as a detector for ionizing radiation. Interactions with the pixels can create enough charge so it will be recorded as a light pulse. Of course you will have to shield it from visible light.

Thank you Nick Proskurin and R. Schnell

Krishnan, I've never heard of medical grade CZT or Ge sensors. It is an overkill, with very low resoution. Since the resolution is the main requirement in medicine, they use various scintillators with CCD device.

Dear Andrey Porokhnyuk ,

x-ray semiconductor detectors are used in pre-clinical and upcoming medical photon counting and spectral CT systems.

See for example :

https://en.wikipedia.org/wiki/Photon-counting_computed_tomography

https://www.google.de/search?source=hp&ei=34T4XqT0LISKasrbltAL&q=photon+counting+spectral+ct&oq=phootn+counting&gs_lcp=CgZwc3ktYWIQARgDMgQIABANMgQIABANMgQIABANMgYIABANEB4yBggAEA0QHjIGCAAQDRAeMgYIABAWEB4yBggAEBYQHjIGCAAQFhAeMgYIABAWEB46BQgAELEDOgIIADoECAAQClCHDFi1KmCffGgAcAB4AIABVogB2giSAQIxNZgBAKABAaoBB2d3cy13aXo&sclient=psy-ab

OK, I agree, that is a kind of new technique not in a wide use today. Any way, scintillators are a few orders cheaper than the cheapest CZT, don't require cryogenics, and are enough for getting a panoramic print of your teeth.

You definitely can, however you should be more specific.

I guess the easiest is to get some small scintillator (e.g. 3x3x5mm BGO or LYSO, can be bought from China) and SipM e.g. MICROFJ-SMA-30035-GEVBOS-ND from Digikey

You can also make alpha particle ( e.g. from Am-241 source used in smoke alarms) detection using silicon photodiode having good access to silicon surface likeConference Paper LOW-COST PHOTODIODE AMPLIFIER FOR ALPHA SPECTROSCOPY

If you implement proper low noise Charge Sensitive Amplifier and use good quality low capacitance, low leakage photodiode you can do X-ray /gamma detection with it too.

http://physicsopenlab.org/2017/09/27/charge-sensitive-preamplifier/

I agree with Erik Strub,

Many thanks to all of you for your suggestion.

Yes we can but when complete our build it must It must be tested to see if it is capable of detection under conditions similar to the conditions of other detectors

Dear Quang Tran Van ,

Welcome!

The most appropriate radiation detector is the pin diode. Its dark current is low and it is quite sensitive to the the incident radiation. There are large area photo diodes that you can try using them as radiation detector.

If you want to increases the detectivity of the diode you can cool down to reduce it dark current.

You can also use chopper to distinguish the radiation from the dark current.

Best wishes