Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Microscopic origin of light emission in Al_yGa_{1-y}N/GaN superlattice:
  Band profile and active site   We present first-principles calculations of AlGaN/GaN superlattice,
clarifying the microscopic origin of the light emission and revealing the
effect of local polarization within the quantum well. Profile of energy band
and distributions of electrons and holes demonstrate the existence of a main
active site in the well responsible for the main band-edge light emission. This
site appears at the position where the local polarization becomes zero. With
charge injection, the calculated optical spectra show that the broadening of
the band gap at the active site leads to the blueshift of emission wavelength.

36
The categories of this paper are: cmp-lg
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
20
The categories of this paper are: acc-phys
6
The categories of this paper are: astro-ph
8
The categories of this paper are: hep-ex
31
The categories of this paper are: ao-sci
16
The categories of this paper are: stat
14
The categories of this paper are: math-ph
21
The categories of this paper are: adap-org
7
The categories of this paper are: hep-th
33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int
18
The categories of this paper are: econ