1 research outputs found
Position-Controlled Uniform GaAs Nanowires on Silicon using Nanoimprint Lithography
We report on the epitaxial growth
of large-area position-controlled
self-catalyzed GaAs nanowires (NWs) directly on Si by molecular beam
epitaxy (MBE). Nanohole patterns are defined in a SiO<sub>2</sub> mask
on 2 in. Si wafers using nanoimprint lithography (NIL) for the growth
of positioned GaAs NWs. To optimize the yield of vertical NWs the
MBE growth parameter space is tuned, including Ga predeposition time,
Ga and As fluxes, growth temperature, and annealing treatment prior
to NW growth. In addition, a non-negligible radial growth is observed
with increasing growth time and is found to be independent of the
As species (i.e., As<sub>2</sub> or As<sub>4</sub>) and the growth
temperatures studied. Cross-sectional transmission electron microscopy
analysis of the GaAs NW/Si substrate heterointerface reveals an epitaxial
growth where NW base fills the oxide hole opening and eventually extends
over the oxide mask. These findings have important implications for
NW-based device designs with axial and radial p–n junctions.
Finally, NIL positioned GaAs/AlGaAs core–shell heterostructured
NWs are grown on Si to study the optical properties of the NWs. Room-temperature
photoluminescence spectroscopy of ensembles of as-grown core–shell
NWs reveals uniform and high optical quality, as required for the
subsequent device applications. The combination of NIL and MBE thereby
demonstrates the successful heterogeneous integration of highly uniform
GaAs NWs on Si, important for fabricating high throughput, large-area
position-controlled NW arrays for various optoelectronic device applications