Molecular beam epitaxial growth of III-V semiconductor ... - KOBRA
Molecular beam epitaxial growth of III-V semiconductor ... - KOBRA
Molecular beam epitaxial growth of III-V semiconductor ... - KOBRA
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MBE Growth <strong>of</strong> InAs and InGaAs Quantum Dots Embedded in GaAs Matrix<br />
related to carrier dynamics in the QDs and have severe inuence on their optical<br />
quality [95, 96]. It has been proposed that these structural defects may be<br />
circumvented by realization <strong>of</strong> <strong>III</strong>/V QDs on the pre-patterned substrates due<br />
to the new lattice and strain adjustments <strong>of</strong> the patterned features [12]. For example,<br />
In(Ga)As QDs <strong>growth</strong> on pre-patterned GaAs substrate is already a well<br />
established eld <strong>of</strong> research due to potential application such as single photon<br />
sources and in quantum electrodynamics. For the large scale fabrication <strong>of</strong> single<br />
quantum light sources, tremendous progress in the <strong>growth</strong> <strong>of</strong> InGaAs QDs on prepatterned<br />
GaAs substrates has been made [97, 98, 99]. Site-controlled InGaAs<br />
QDs with very narrow linewidth photoluminescence signal have been achieved<br />
both in inverted pyramidal [101, 102] and circular nanoholes [100, 103]. This<br />
represents a good motivation to use this approach also for <strong>III</strong>-V QDs on silicon.<br />
6.2 MBE Growth <strong>of</strong> SA-InAs Quantum Dots Embedded<br />
in Thin GaAs Matrix on Flat Silicon<br />
Substrate<br />
6.2.1 GaAs on Silicon Epitaxy<br />
The direct epitaxy <strong>of</strong> GaAs on silicon substrates was subject <strong>of</strong> research over the<br />
last two decades. Recent successful approaches are mainly based on the <strong>growth</strong> <strong>of</strong><br />
thick relaxed GaAs buer layer, which is normally composed <strong>of</strong> two steps <strong>growth</strong><br />
at two dierent <strong>growth</strong> temperatures [9, 104, 105]. On the other hand, inserting<br />
an intermediate layer between GaAs and silicon like GeSi or short period super<br />
lattice (used as strain lter) represent another alternative successful integration<br />
<strong>of</strong> GaAs with silicon [106, 108]. However, our new approach is based on using the<br />
islands <strong>growth</strong> mode <strong>of</strong> GaAs, at the initial nucleation stage prior to the active<br />
layer <strong>growth</strong>.<br />
However, dierent studies have been demonstrated that at the<br />
early stages <strong>of</strong> GaAs-on-Si epitaxy involves no wetting layer [109, 110, 96]; GaAs<br />
islands form directly on the substrate and, hence, the initial <strong>growth</strong> mechanism is<br />
Volmer Weber, in which the islanding <strong>of</strong> the lm occurs because <strong>of</strong> the energetic<br />
favorability <strong>of</strong> low GaAs coverage (few monolayers) <strong>growth</strong> on Si . According<br />
104