Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nanometre scale monitoring of the quantum confined stark effect and
  emission efficiency droop in multiple GaN/AlN quantum disks in nanowires   We report on a detailed study of the intensity dependent optical properties
of individual GaN/AlN Quantum Disks (QDisks) embedded into GaN nanowires (NW).
The structural and optical properties of the QDisks were probed by high spatial
resolution cathodoluminescence (CL) in a scanning transmission electron
microscope (STEM). By exciting the QDisks with a nanometric electron beam at
currents spanning over 3 orders of magnitude, strong non-linearities (energy
shifts) in the light emission are observed. In particular, we find that the
amount of energy shift depends on the emission rate and on the QDisk morphology
(size, position along the NW and shell thickness). For thick QDisks (>4nm), the
QDisk emission energy is observed to blue-shift with the increase of the
emission intensity. This is interpreted as a consequence of the increase of
carriers density excited by the incident electron beam inside the QDisks, which
screens the internal electric field and thus reduces the quantum confined Stark
effect (QCSE) present in these QDisks. For thinner QDisks (<3 nm), the
blue-shift is almost absent in agreement with the negligible QCSE at such
sizes. For QDisks of intermediate sizes there exists a current threshold above
which the energy shifts, marking the transition from unscreened to partially
screened QCSE. From the threshold value we estimate the lifetime in the
unscreened regime. These observations suggest that, counterintuitively,
electrons of high energy can behave ultimately as single electron-hole pair
generators. In addition, when we increase the current from 1 pA to 10 pA the
light emission efficiency drops by more than one order of magnitude. This
reduction of the emission efficiency is a manifestation of the efficiency droop
as observed in nitride-based 2D light emitting diodes, a phenomenon tentatively
attributed to the Auger effect.

16
The categories of this paper are: stat
17
The categories of this paper are: q-fin
9
The categories of this paper are: nlin
6
The categories of this paper are: astro-ph
19
The categories of this paper are: eess
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
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The categories of this paper are: adap-org
18
The categories of this paper are: econ
3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph
30
The categories of this paper are: q-alg
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The categories of this paper are: dg-ga
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The categories of this paper are: math-ph
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The categories of this paper are: supr-con