471 research outputs found
Growth and structural characterization of pyramidal site-controlled quantum dots with high uniformity and spectral purity
This work presents some fundamental features of pyramidal site-controlled
InGaAs Quantum Dots (QDs) grown by MetalOrganic Vapour Phase Epitaxy on
patterned GaAs (111)B substrate. The dots self-form inside pyramidal recesses
patterned on the wafer via pre-growth processing. The major advantage of this
growth technique is the control it provides over the dot nucleation posi-tion
and the dimensions of the confined structures onto the sub-strate. The
fundamental steps of substrate patterning and the QD forma-tion mechanism are
described together with a discussion of the structural particulars. The
post-growth processes, including sur-face etching and substrate removal, which
are required to facili-tate optical characterization, are discussed. With this
approach extremely high uniformity and record spectral purity are both
achieved
Relevance of the purity level in a MetalOrganic Vapour Phase Epitaxy reactor environment for the growth of high quality pyramidal sitecontrolled Quantum Dots
We report in this work on the spectral purity of pyramidal site-controlled
InGaAs/AlGaAs Quantum Dots grown by metalorganic vapour phase epitaxy on(111)B
oriented GaAs substrates. Extremely sharp emission peaks were found, showing
linewidths surprisingly narrow (~27{\mu}eV) and comparable to those which can
be obtained by Molecular Beam Epitaxy in an ultra-high vacuum environment. A
careful reactor handling is regarded as a crucial step toward the fabrication
of high optical quality systems.Comment: ICMOVPE 2010 Proceedin
A site-controlled quantum dot system offering both high uniformity and spectral purity
In this paper we report on the optical properties of site controlled InGaAs
dots with GaAs barriers grown in pyramidal recesses by metalorganic vapour
phase epitaxy. The inhomogeneous broadening of excitonic emission from an
ensemble of quantum dots is found to be unusually narrow, with a standard
deviation of 1.19 meV, and spectral purity of emission lines from individual
dots is found to be very high (18-30 ueV), in contrast with other
site-controlled systems.Comment: 12 pages, 3 figure
From Healing Rituals to Music Therapy: Bridging the Cultural Divide Between Therapist and Young Sudanese Refugees
In music therapy literature and popular culture alike, music is often hailed as a universal language. It is appropriate then that music therapy is included within the services offered at a high school catering specifically to non-English-speaking students. The music therapy program described in this paper encourages students to explore and express their feelings by playing instruments, singing, writing songs, listening to music and talking about song lyrics. The school is state-run (but federally funded) and provides English language, high school preparation and settlement services to high school aged youth who have recently arrived in Australia from non-English-speaking countries. There are currently 22 nationalities represented amongst the student population, with most students staying no longer than six months before being integrated into mainstream schools with English as a Second Language (ESL) support. While some of the students' families are business migrants, some 60% of students have arrived in Australia as refugees. An increasing proportion (currently 41.6%) originated from The Republic of the Sudan in northern Africa
AlGaAs/GaAs/AlGaAs quantum wells as a sensitive tool for the MOVPE reactor environment
We present in this work a simple Quantum Well (QW) structure consisting of
GaAs wells with AlGaAs barriers as a probe for measuring the performance of
arsine purifiers within a MetalOrganic Vapour Phase Epitaxy system. Comparisons
between two different commercially available purifiers are based on the
analysis of low temperature photoluminescence emission spectra from thick QWs,
grown on GaAs substrates misoriented slightly from (100). Neutral excitons
emitted from these structures show extremely narrow linewidths, comparable to
those which can be obtained by Molecular Beam Epitaxy in an ultra-high vacuum
environment, suggesting that purifications well below the 1ppb level are needed
to achieve high quality quantum well growth
Low-angle misorientation dependence of the optical properties of InGaAs/InAlAs quantum wells
We investigate the dependence of the low-temperature photoluminescence
linewidths from InP-lattice-matched InGaAs/InAlAs quantum wells on the
low-angle misorientation from the (100) surface of the host InP substrate.
Quantum wells were grown on InP substrates misorientated by 0, 0.2, 0.4 and 0.6
degrees; 0.4 degrees was found to consistently result in the narrowest peaks,
with the optimal spectral purity of ~4.25 meV found from a 15nm quantum well.
The width of the emission from the 15nm quantum well was used to optimize the
growth parameters. Thick layers of Si-doped InGaAs were then grown and found to
have bulk, low temperature (77 K), electron mobilities up to \mu ~ 3.5 x 10^4
cm2/Vs with an electron concentration of ~1 x 10^16
Impact of Nitrogen incorporation on pseudomorphic site-controlled quantum dots grown by Metalorganic Vapour Phase Epitaxy
We report on some surprising optical properties of diluted nitride
InGaAs_(1-y)N_y /GaAs (y<<1) pyramidal site-controlled quantum dots, grown by
metalorganic vapor phase epitaxy on patterned GaAs (111)B substrates.
Microphotoluminescence characterizations showed antibinding exciton/ biexciton
behavior, a spread of exciton lifetimes in an otherwise very uniform sample,
with unexpected long neutral exciton lifetimes (up to 7 ns) and a nearly zero
fine structure splitting on a majority of dots
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