Molecular beam epitaxial growth of GaSb/GaAs quantum dots on Ge substrates

Kunrugsa, Maetee; Kiravittaya, Suwit; Sopitpan, Suwat; Ratanathammaphan, Somchai; Panyakeow, Somsak

doi:10.1016/j.jcrysgro.2014.02.048

Cited by 13 publications

(6 citation statements)

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“…with a standard deviation σ = 40 meV. This value is derived from the photoluminescence (PL) spectrum linewidth of ∼ 100 meV [52] by the relation that the linewidth equals 2σ √ 2 ln 2. However, σ = 4 meV is applied to the case of single QD.…”

Section: Absorption Coefficientmentioning

confidence: 99%

Optical absorption coefficient calculations of GaSb/GaAs quantum dots for intermediate band solar cell applications

Kunrugsa¹

2020

J. Phys. D: Appl. Phys.

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Absorption coefficients of GaSb/GaAs quantum dots (QDs) are calculated by the 8-band strain-dependent k· p method and Fermi’s golden rule. A more realistic but simple approach to model the QD ensemble with wetting layer is described. Effects of the QD size and density, and the GaAs spacer thickness for multi-stacked QDs on absorption characteristics are studied. Absorption spectra of the single QD, single layer of QDs, and multi-stacked QDs are presented and discussed. Interband absorption is found to be more intense than intraband absorption. The calculated absorption spectra are brought into the drift-diffusion model coupled with rate equations to determine the current density-voltage curves of the GaSb/GaAs QD solar cells, which are compared with measured data in literature for validation. The models proposed in this work are capable of predicting the short-circuit current density and open-circuit voltage of real devices, and would have the potential to investigate the impact of doping and position of the QD layers, which is necessary for intermediate band solar cell analysis and design.

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Section: Absorption Coefficientmentioning

confidence: 99%

Optical absorption coefficient calculations of GaSb/GaAs quantum dots for intermediate band solar cell applications

Kunrugsa¹

2020

J. Phys. D: Appl. Phys.

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“…However, such layer thicknesses and doping levels are not optimized. According to the experimental data, the GaSb QDs grown on the GaAs surface are dome-shaped and have an average diameter and height of 90 and 6 nm, respectively, and a density of approximately 1.7 × 10 10 cm −2 [33]. The incorporation of As into the GaSb QDs can change their shape and density, or even turn them into QRs, depending on the growth conditions [34][35][36].…”

Section: Modeling and Simulationmentioning

confidence: 99%

Two-dimensional simulation of GaAsSb/GaAs quantum dot solar cells

Kunrugsa¹

2018

J. Phys. D: Appl. Phys.

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Two-dimensional (2D) simulation of GaAsSb/GaAs quantum dot (QD) solar cells is presented. The effects of As mole fraction in GaAsSb QDs on the performance of the solar cell are investigated. The solar cell is designed as a p-i-n GaAs structure where a single layer of GaAsSb QDs is introduced into the intrinsic region. The current density–voltage characteristics of QD solar cells are derived from Poisson’s equation, continuity equations, and the drift-diffusion transport equations, which are numerically solved by a finite element method. Furthermore, the transition energy of a single GaAsSb QD and its corresponding wavelength for each As mole fraction are calculated by a six-band k · p model to validate the position of the absorption edge in the external quantum efficiency curve. A GaAsSb/GaAs QD solar cell with an As mole fraction of 0.4 provides the best power conversion efficiency. The overlap between electron and hole wave functions becomes larger as the As mole fraction increases, leading to a higher optical absorption probability which is confirmed by the enhanced photogeneration rates within and around the QDs. However, further increasing the As mole fraction results in a reduction in the efficiency because the absorption edge moves towards shorter wavelengths, lowering the short-circuit current density. The influences of the QD size and density on the efficiency are also examined. For the GaAsSb/GaAs QD solar cell with an As mole fraction of 0.4, the efficiency can be improved to 26.2% by utilizing the optimum QD size and density. A decrease in the efficiency is observed at high QD densities, which is attributed to the increased carrier recombination and strain-modified band structures affecting the absorption edges.

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“…It is therefore of interest to investigate structural properties of obtained QDs under various growth conditions in order to fine-tune them for any specific applications. In literature, different GaSb QD shapes have been reported [7,8]. For example, Jiang et al [7] have shown that the elongation of GaSb QDs along the [1 1 0] direction can be controlled by changing the V/III ratio.…”

Section: Introductionmentioning

confidence: 99%