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Theoretical and experimental investigations of vertical hole transport through unipolar AlGaN structures: Impacts of random alloy disorder
We report on the vertical hole transport through unipolar unintentionally doped (UID) and p-type doped AlGaN heterostructures to evaluate the effectiveness of the UID and doped AlGaN as barriers to the hole transport. Band diagram and current density–voltage (J–V) simulations are conducted in one-di...
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Published in: | Applied physics letters 2020-07, Vol.117 (2) |
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Main Authors: | , , , , , |
Format: | Article |
Language: | English |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | We report on the vertical hole transport through unipolar unintentionally doped (UID) and
p-type doped AlGaN heterostructures to evaluate the effectiveness of
the UID and doped AlGaN as barriers to the hole transport. Band diagram and current
density–voltage (J–V) simulations are conducted in one-dimensional and
three-dimensional schemes, with the latter including compositional fluctuations within the
alloy AlGaN barrier layer. The simulation results using a self-consistent Poisson-drift
diffusion scheme, incorporating the Localization Landscape theory, indicate a large
asymmetric barrier to the hole transport by UID AlGaN. The asymmetric J–V
characteristics are attributed to the asymmetric band diagrams calculated for the unipolar
structure. The simulation results are verified by experiments using unipolar vertical hole
transport structures enabled by n-to-p tunnel junctions
(TJs) grown by ammonia molecular-beam epitaxy. The TJ structures are utilized to minimize
the issues with the high spreading resistance of p-regions and to
eliminate the need for its dry etching, which normally results in degraded
p-contacts. The experimental results show that even a thin UID
AlxGa1−xN (x = 14%, 13 nm) introduces an asymmetric barrier to the
hole transport; a nearly 100% increase in the voltage drop induced by a thin UID AlGaN at
50 A/cm2 in the reverse direction is observed compared to an only 25%
corresponding increase in the forward direction. Furthermore, p-type
doping of the AlGaN layer results in a drastic drop in the potential barrier to hole
transport in both directions. The results are beneficial for understanding the behavior of
various structure designs within optoelectronics and power electronics. |
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ISSN: | 0003-6951 1077-3118 |
DOI: | 10.1063/5.0006291 |