Monday, December 12, 2016

Pixpolar Technology in PhD Thesis

Lappeenranta University of Technology (LUT), Finland, publishes PhD Thesis "Novel Solutions for Improving Solid-State Photon Detector Performance and Manufacturing" by Vladislav Marochkin. The thesis discusses Pixpolar MIG pixel, silicon drift detectors, and 3D radiation detectors. The doctoral dissertation defense is scheduled for December 15, 2016. A discussion of operational principles of the photon detectors starts with an interesting quote on page 17:

"When a photon interacts with silicon it creates electron-hole pairs, the amount of which is dependent on photon energy. “The energy required to create an electron-hole pair in silicon is 3.6 eV. The band gap of silicon is 1.12 eV at room temperature and the average energy needed to create a single pair, called the radiation ionization energy, is empirically found to be about three times the band gap energy of the semiconductor. This is due to the phonon excitation, which is required for momentum conservation” (Luukka, 2006)."


  1. But every coin has two sides, also here is some good news to find : there remains a need for training in the field of solid-state imaging, even for the fundamental physics of it !

    1. Albert, it should be really a hard job for you :)-

  2. Has a MIGFET image sensor ever been produced or demoed?

  3. The 3.6eV energy is very well known by people working in high energy particle detection and radiation effects. I would not call it the energy required to create and electron-hole pair since as everybody knows the absoprtion of a 1.12eV can lead to the generation of an electron-hole pair.
    This 3.6eV energy is generally described as the empirical ratio between the total energy deposited in the considered silicon volume by a high energy photon (start to be valid for X-rays, and possibly some EUV photons I guess) to the number of effectively generated electron hole pairs (after relaxation of the primary generated electrons, i.e. the effective number of free carriers you get a significant time after the interaction).
    So its an average energy per effectively created electron hole pair when a high energy photon is absorbed in the silicon (and thus when a large number of electron-hole pairs are created localy). As far as I remember it includes many physical mechanisms of energy loss (phonon interactions but also electron-electron interactions and many more).
    I don't think it applies to visible photons and I think the following comment is misleading (and most likely wrong): "This is due to the phonon excitation, which is required for momentum conservation"

  4. Please note that for a 1000nm photon that can create a electron/hole pair, its enery is around 1.2eV; very close to the bandgap of the Si at room temperature. Please take care with this comments in a specialized blog like this.


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