Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 2D-subband spectra variations under persistent tunneling
  photoconductivity condition in tunnel delta-GaAs/Al structures   2DEG states of Al/$\delta$-GaAs structures were investigated in the
persistent tunneling photoconductivity (PTPC) regime at low temperatures.
"Thickening" of the unoccupied subbands to the ground state of 2DEG was
observed at $T=4.2$~$K$. It was found that there is a uniform shift of the
subband levels at $T=77$~$K$. The behavior of the persistent 2D states in
tunneling spectra after various illumination and at different temperatures
allows us to assume that there are two PTPC mechanisms, namely, the broadening
of the potential well profile of the $\delta$-layer and photoionization of the
DX-centers.

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The categories of this paper are: alg-geom
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The categories of this paper are: chao-dyn
13
The categories of this paper are: quant-ph
14
The categories of this paper are: math-ph
1
The categories of this paper are: cs
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The categories of this paper are: dg-ga
3
The categories of this paper are: physics
6
The categories of this paper are: astro-ph
17
The categories of this paper are: q-fin
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The categories of this paper are: supr-con
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The categories of this paper are: funct-an
33
The categories of this paper are: plasm-ph
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The categories of this paper are: chem-ph
19
The categories of this paper are: eess
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The categories of this paper are: adap-org
16
The categories of this paper are: stat