Luminous Efficiency of Axial In<sub><i>x</i></sub>Ga<sub>1–<i>x</i></sub>N/GaN Nanowire Heterostructures:
Interplay of Polarization and Surface Potentials
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Abstract
Using
continuum elasticity theory and an eight-band <b>k</b>·<b>p</b> formalism, we study the electronic properties
of GaN nanowires with axial In<sub><i>x</i></sub>Ga<sub>1–<i>x</i></sub>N insertions. The three-dimensional
strain distribution in these insertions and the resulting distribution
of the polarization fields are fully taken into account. In addition,
we consider the presence of a surface potential originating from Fermi
level pinning at the sidewall surfaces of the nanowires. Our simulations
reveal an in-plane spatial separation of electrons and holes in the
case of weak piezoelectric potentials, which correspond to an In content
and layer thickness required for emission in the blue and violet spectral
range. These results explain the quenching of the photoluminescence
intensity experimentally observed for short emission wavelengths.
We devise and discuss strategies to overcome this problem