InAs/GaAs quantum dots (QDs) embedded within InP/GaP nanowires (NWs)
were grown on Si substrates by Au-assisted and self-assisted vapor-liquid-solid
(VLS) growth using molecular beam epitaxy (MBE). The morphology and
structure of the NWs was characterized using scanning electron microscopy
(SEM) and transmission electron microscopy (TEM). The samples were analysed
using photoluminescence (PL) and photocurrent measurements to study the
properties of NW-based QDs.
The composition of InAs x P 1-x QDs embedded within InP NWs was varied
from x = 0.25 to x = 1, demonstrating the tuning of quantum confined energy
levels. PL measurements demonstrated an emission peak that shifted towards
lower energy levels as the As composition was increased. This result was also
observed for QD absorption peaks through wavelength-dependent room
temperature photocurrent measurements. InP NWs were successfully passivated
with an AlInP shell, which was demonstrated through PL analysis.
The growth mechanism of patterned self-assisted GaP NWs on Si was studied
through SEM and TEM analysis. It was found that for large V/III flux ratios the
Ga seed particle reduced in volume throughout growth, which led to a smaller
NW diameter. Conversely, for small V/III flux ratios the Ga seed particle
increased in volume throughout growth, resulting in larger NW diameters. The
dependence of V/III flux ratio on NW growth was characterized, allowing the
tuning of NW diameter.
iv
GaP NWs with p-i-n junctions were fabricated on a Si substrate with GaAs
QDs embedded within the intrinsic region. To the author’s knowledge, this is the
first time such a device was demonstrated. The device demonstrated diode
characteristics as expected for a p-n junction. Wavelength-dependent photocurrent
measurements demonstrated the absorption of light within GaAs QDs, which was
collected through electric field dependent tunneling and thermionic emission. The
absorption of light extended beyond the bandgap of GaP due to the GaAs QDs. / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/22735 |
| Date | 24 November 2017 |
| Creators | Kuyanov, Paul |
| Contributors | LaPierre, Ray, Engineering Physics |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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