Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Challenges and opportunities of ZnO-related single crystalline
  heterostructures   Recent technological advancement in ZnO heterostructures has expanded the
possibility of device functionalities to various kinds of applications. In
order to extract novel device functionalities in the heterostructures, one
needs to fabricate high quality films and interfaces with minimal impurities,
defects, and disorder. With employing molecular-beam epitaxy (MBE) and single
crystal ZnO substrates, the density of residual impurities and defects can be
drastically reduced and the optical and electrical properties have been
dramatically improved for the ZnO films and heterostructures with MgxZn1-xO.
Here, we overview such recent technological advancement from various aspects of
application. Towards optoelectronic devices such as a light emitter and a
photodetector in an ultraviolet region, the development of p-type ZnO and the
fabrication of excellent Schottky contact, respectively, have been subjected to
intensive studies for years. For the former, the fine tuning of the growth
conditions to make MgxZn1-xO as intrinsic as possible has opened the
possibilities of making p-type MgxZn1-xO through NH3 doping method. For the
latter, conducting and transparent polymer films spin-coated on MgxZn1-xO was
shown to give almost ideal Schottky junctions. The wavelength-selective
detection can be realized with varying the Mg content. From the viewpoint of
electronic devices, two-dimensional electrons confined at the MgxZn1-xO/ZnO
interfaces are promising candidate for quantum devices because of high electron
mobility and strong electron-electron correlation effect. These wonderful
features and tremendous opportunities in ZnO-based heterostructures make this
system unique and promising in oxide electronics and will lead to new quantum
functionalities in optoelectronic devices and electronic applications with
lower energy consumption and high performance.

14
The categories of this paper are: math-ph
23
The categories of this paper are: solv-int
0
The categories of this paper are: hep-ph
3
The categories of this paper are: physics
15
The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
18
The categories of this paper are: econ
10
The categories of this paper are: q-bio
24
The categories of this paper are: dg-ga
5
The categories of this paper are: gr-qc
27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
28
The categories of this paper are: alg-geom
11
The categories of this paper are: hep-lat
1
The categories of this paper are: cs