This work reports on theoretical and experimental investigation of the impact of InAs quantum dots (QDs) position with respect to InGaAs strain reducing layer (SRL). The investigated samples are grown by molecular beam epitaxy and characterized by photoluminescence spectroscopy (PL). The QDs optical transition energies have been calculated by solving the three dimensional Schrödinger equation using the finite element methods and taking into account the strain induced by the lattice mismatch. We have considered a lens shaped InAs QDs in a pure GaAs matrix and either with InGaAs strain reducing cap layer or underlying layer. The correlation between numerical calculation and PL measurements allowed us to track the mean buried QDs size evolution with respect to the surrounding matrix composition. The simulations reveal that the buried QDs’ realistic size is less than that experimentally driven from atomic force microscopy observation. Furthermore, the average size is found to be slightly increased for InGaAs capped QDs and dramatically decreased for QDs with InGaAs under layer.
This paper investigates the impact of the deposition rate on the mean buried InAs/GaAs quantum dots’ (QDs) size by means of a coupled photoluminescence spectroscopy and numerical approach. The proposed method consists in tuning the theoretical transition energies by changing the QDs aspect ratio towards best fit of the photoluminescence emission energies arising from the state filling effect. The electron-hole confined states are obtained by solving the single particle one band effective mass Schrödinger equation in cylindrical coordinates for a lens shaped QD by finite element method taking into account the strain effects. The obtained evolution is in agreement with morphological data taken from similar uncapped QDs samples.
In this work, we have theoretically investigated the intermixing effect in highly strained In 0.3 Ga 0.7 As/GaAs quantum well (QW) taking into consideration the composition profile change resulting from in-situ indium surface segregation. To study the impact of the segregation effects on the postgrowth intermixing, one dimensional steady state Schrodinger equation and Fick's second law of diffusion have been numerically solved by using the finite difference methods. The impact of the In/Ga interdiffusion on the QW emission energy is considered for different In segregation coefficients. Our results show that the intermixed QW emission energy is strongly dependent on the segregation effects. The interdiffusion enhanced energy shift is found to be considerably reduced for higher segregation coefficients. This work adds a considerable insight into the understanding and modelling of the effects of interdiffusion in semiconductor nanostructures.
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