Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hydride Vapor Phase Epitaxy of GaN on Silicon Covered by Nanostructures   Several ten $\mu$m GaN have been deposited on a silicon substrate using a
two-step hydride vapor phase epitaxy (HVPE) process. The substrates have been
covered by AlN layers and GaN nanostructures grown by plasma-assisted
molecular-beam epitaxy. During the first low-temperature (low-T) HVPE step,
stacking faults (SF) form, which show distinct luminescence lines and
stripe-like features in cathodoluminescence images of the cross-section of the
layers. These cathodoluminescence features allow for an insight into the growth
process. During a second high-temperature (high-T) step, the SFs disappear, and
the luminescence of this part of the GaN layer is dominated by the donor-bound
exciton. For templates consisting of both a thin AlN buffer and GaN
nanostructures, a silicon incorporation into the GaN grown by HVPE is not
observed. Moreover, the growth mode of the (high-T) HVPE step depends on the
specific structure of the AlN/GaN template, where in a first case, the epitaxy
is dominated by the formation of slowly growing facets, while in a second case,
the epitaxy proceeds directly along the c-axis.

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The categories of this paper are: eess
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The categories of this paper are: plasm-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: cs
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The categories of this paper are: hep-th
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The categories of this paper are: econ
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-ph
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The categories of this paper are: supr-con
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The categories of this paper are: funct-an
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The categories of this paper are: math
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The categories of this paper are: stat
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The categories of this paper are: astro-ph