Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Growth and optical properties of GaN/AlN quantum wells   We demonstrate the growth of GaN/AlN quantum well structures by
plasma-assisted molecular-beam epitaxy by taking advantage of the surfactant
effect of Ga. The GaN/AlN quantum wells show photoluminescence emission with
photon energies in the range between 4.2 and 2.3 eV for well widths between 0.7
and 2.6 nm, respectively. An internal electric field strength of $9.2\pm 1.0$
MV/cm is deduced from the dependence of the emission energy on the well width.

31
The categories of this paper are: ao-sci
13
The categories of this paper are: quant-ph
0
The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
5
The categories of this paper are: gr-qc
35
The categories of this paper are: mtrl-th
30
The categories of this paper are: q-alg
29
The categories of this paper are: funct-an
15
The categories of this paper are: nucl-ex
33
The categories of this paper are: plasm-ph
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys
8
The categories of this paper are: hep-ex
36
The categories of this paper are: cmp-lg