Dear Aydin Amini

I recommend you to give a little more context to your question. Did you read about this in some publication?

Dear Kai Fauth

I appreciate your attention...

Recently I read about the optical properties of a-IGZO. The article states that the amorphous IGZO contains weakly bonded oxygen and by photon excitation, these oxygen ions can easily hop and a metastable donor state is formed. This metastable state lowers the electron hole recombination.

The problem is that I don't know any mechanism that responsible for this phenomena.... Should I treat the metastable state as a recombination center or some lattice flaws ???

Let me inervene once more. Since indeed, the topic and mechanism seem a bit peculiar, make it easy for your peers to access the information right where you found it, be it by correct bibliographic citation, by a link to the paper at the journal site (better), by researching whether the paper is (also) available on RG or some preprint server (even better).

That will it make more easy for others to find what they need to know if they find the topic interesting and you'll be more likely to find colleagues to discuss your problem with.

Here is the link:

http://ieeexplore.ieee.org/stamp/stamp.jsptp=&arnumber=8333736&isnumber= 361595

doi: 10.1109/LED.2018.2824339

The metastable formation process have been addressed on page 2. You can access easily by searching for "hop" keyword.

Their last author is on RG (Qing Wan). You could try to contact him. I have no access to that paper. Do they introduce the mechanism which bothers you in this very paper or are they referring to other work in the literature?

Only the Persistent Photoconductivity result of metastable stage reffed to following article

Article Large Photoresponse in Amorphous In–Ga–Zn–O and Origin of Re...

but the given explanation for metastable formation is no convincing...