1,260 research outputs found
Growth kinetics effects on self-assembled InAs/InP quantum dots
A systematic manipulation of the morphology and the optical emission
properties of MOVPE grown ensembles of InAs/InP quantum dots is demonstrated by
changing the growth kinetics parameters. Under non-equilibrium conditions of a
comparatively higher growth rate and low growth temperature, the quantum dot
density, their average size and hence the peak emission wavelength can be tuned
by changing efficiency of the surface diffusion (determined by the growth
temperature) relative to the growth flux. We further observe that the
distribution of quantum dot heights, for samples grown under varying
conditions, if normalized to the mean height, can be nearly collapsed onto a
single Gaussian curve.Comment: 2 figure
Distorted wurtzite unit cells: Determination of lattice parameters of non-polar a-plane AlGaN and estimation of solid phase Al content
Unlike c-plane nitrides, ``non-polar" nitrides grown in e.g. the a-plane or
m-plane orientation encounter anisotropic in-plane strain due to the anisotropy
in the lattice and thermal mismatch with the substrate or buffer layer. Such
anisotropic strain results in a distortion of the wurtzite unit cell and
creates difficulty in accurate determination of lattice parameters and solid
phase group-III content (x_solid) in ternary alloys. In this paper we show that
the lattice distortion is orthorhombic, and outline a relatively simple
procedure for measurement of lattice parameters of non-polar group III-nitrides
epilayers from high resolution x-ray diffraction measurements. We derive an
approximate expression for x_solid taking into account the anisotropic strain.
We illustrate this using data for a-plane AlGaN, where we measure the lattice
parameters and estimate the solid phase Al content, and also show that this
method is applicable for m-plane structures as well
Facile fabrication of lateral nanowire wrap-gate devices with improved performance
We present a simple fabrication technique for lateral nanowire wrap-gate
devices with high capacitive coupling and field-effect mobility. Our process
uses e-beam lithography with a single resist-spinning step, and does not
require chemical etching. We measure, in the temperature range 1.5-250 K, a
subthreshold slope of 5-54 mV/decade and mobility of 2800-2500 --
significantly larger than previously reported lateral wrap-gate devices. At
depletion, the barrier height due to the gated region is proportional to
applied wrap-gate voltage.Comment: 3 pages, 3 figure
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