In this thesis, the effect of surfactants (Bi /Sb) on GaAs(111) is explored, particularly
in regards to modifying the surface morphology and growth kinetics. Both molecular beam epitaxy (MBE) and metal-organic chemical vapour deposition (MOCVD)
techniques are discussed in this context. InAs/GaAs(111) quantum dots (QDs) have
been promoted as leading candidates for efficient entangled photon sources, owing
to their high degree of symmetry (c_3v). Unfortunately, GaAs(111) suffers from a
defect-ridden homoepitaxial buffer layer, and the InAs/GaAs(111) material system
does not natively support Stranski{Krastanov InAs QD growth. Surfactants have
been identified as effective tools to alter grown surface morphologies and growth
modes, potentially overcoming these obstacles, but have yet to be studied in detail
in this context. For MBE, it is shown that Bi acts as a surfactant when employed in
GaAs(111) homoepitaxy, and eliminates defects/hillocks, yielding atomically-smooth
surfaces with step-flow growth, and RMS roughness values of 0.13 nm. The effect
is more pronounced as the Bi flux increases, and Bi is suggested to be increasing
adatom diffusion. A novel reflection high energy electron diffraction (RHEED)-based
experiment was also designed and performed to measure the desorption activation
energy (U_Des) of Bi on GaAs(111), yielding U_Des = 1.74 ± 0.38 eV. GaAs(111) homoepitaxy was also investigated using MOCVD, with GaAs(111)B exhibiting RMS roughness values of 0.09 nm. Sb is shown to provoke a morphological transition from
plastically-relaxed 2D to 3D growth for InAs/GaAs(111)B, showing promise in its
ability to induce QDs. Finally, simulations for GaAs-based quantum well (QW) photoluminescence were conducted, and such QWs are shown to potentially produce very
sharp linewidths of 3.9 meV. These results enhance understanding of Bi surfactant
behaviour on GaAs(111) and can open up its use in many technological applications,
paving the way for the realization of high efficiency/viable QD entangled photon
sources. / Thesis / Master of Applied Science (MASc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/26918 |
| Date | January 2021 |
| Creators | Hassanen, Ahmed |
| Contributors | Lewis, Ryan, Engineering Physics |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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