Can the concept of the N-face or the Ga-face exist when the GaN film is not a single crystal anymore but a polycrystalline film? Can there be something like a net polarity in poly films?
Polarity does not depend on single or polycrystallinity. But I see your point. However, finally it is like with all properties of polycrystalline materials an anisotropy. The texture reflects you, how big will be the effective polarity.
As polarity refers to specific crystal orientations, I would not call it a net polarity, but a net polarization charge.
...which is quite irritating. Assuming a cubic AB semiconductor, and the structure is defined in a way that (111) is an A-face, then (113) is a B-face, and (115) an A-face again. This happens in GaN as well. In a crystallographic zone A-, non-polar and B-faces exist.
Thanks for your answer. "The texture reflects you, how big will be the effective polarity."...i get an idea now.
In the same thread...if i have a crystalline GaN with a certain polarity. And now i start to depth profile the crystal by sputtering Ar ions into it. Then i would be destroying the surface polarity, isn't it?
I am asking this because, XPS has been used to identify GaN polarity (more tendency of the Ga-face to oxidize). But probably only surface XPS works for this purpose and not thedepth profiled data. If i look into my depth profiled XPS data, would i be able to comment on the polarity?
Polarity is not defined on the surface but in the bulk crystal. The surface itself, though, is subjected to reconstruction, Ga adlayers, oxidation... which gives you a variation of the dipole moment at the surface.
Hi Martin, yes polarity is indeed defined in the bulk crystal. but in the ideal world (although nothing is) the surface will also follow the polarity of the bulk. then XPS can be used as a tool to identify the polarity...
now my doubt was, if you sputter and etch through the crystal to collect depth profile XPS data (just say to obtain the composition) then you are also destroying the crystal lattice during sputtering. so depth profile XPS should not be a tool for checking the polarity.
is it or isn't it? :)
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