2 research outputs found
Luminous Efficiency of Axial In<sub><i>x</i></sub>Ga<sub>1â<i>x</i></sub>N/GaN Nanowire Heterostructures: Interplay of Polarization and Surface Potentials
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>1â<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
Crystal-Phase Quantum Wires: One-Dimensional Heterostructures with Atomically Flat Interfaces
In
semiconductor quantum-wire heterostructures, interface roughness
leads to exciton localization and to a radiative decay rate much smaller
than that expected for structures with flat interfaces. Here, we uncover
the electronic and optical properties of the one-dimensional extended
defects that form at the intersection between stacking faults and
inversion domain boundaries in GaN nanowires. We show that they act
as crystal-phase quantum wires, a novel one-dimensional quantum system
with atomically flat interfaces. These quantum wires efficiently capture
excitons whose radiative decay gives rise to an optical doublet at
3.36 eV at 4.2 K. The binding energy of excitons confined in crystal-phase
quantum wires is measured to be more than twice larger than that of
the bulk. As a result of their unprecedented interface quality, these
crystal-phase quantum wires constitute a model system for the study
of one-dimensional excitons