Atomistic analysis of the impact of alloy and well-width fluctuations on the electronic and optical properties of InGaN/GaN quantum wells

Schulz, Stefan; Miguel, A.; Coughlan, Conor; O’Reilly, Eoin P.

doi:10.1103/physrevb.91.035439

Cited by 119 publications

(168 citation statements)

References 59 publications

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“…For electrons we find a standard deviation of σ e = 9.8 meV, while the standard deviation for the hole ground state energy is σ h = 33.7 meV. We have observed a similar behavior in c-plane (In,Ga)N/GaN QWs [35].…”

Section: Theoretical Results: Electronic Structure and Optical Prosupporting

confidence: 63%

“…The model has already been benchmarked against experimental and DFT data on bulk (In,Ga)N alloys, revealing a very good agreement between experiment, DFT, and TB results [52]. Moreover, our recent calculations on electronic and optical properties of c-plane (In,Ga)N/GaN QWs show also a very good agreement with available experimental data [35]. The model can directly be applied, without modification of the theoretical framework, to m-plane structures.…”

Section: Theoretical Frameworksupporting

confidence: 63%

“…The strong variations in the hole ground state energies in cplane systems are attributed to hole wave function localization effects due to random alloy fluctuations [28,29,35]. To confirm this behavior in a nonpolar system, Fig.…”

Section: Gs and Holementioning

confidence: 99%

“…This approach allows us to include (random) alloy fluctuations in the QW region and the resulting local strain and built-in potential fluctuations on a microscopic level. The strain field calculations are based on a modified valence force field model accounting for electrostatic corrections in addition to bond bending, bond stretching, and related cross-terms [35]. Local built-in field fluctuations are treated on the basis of our recently developed local polarization theory [52].…”

Section: Theoretical Frameworkmentioning

confidence: 99%

“…These effects could be very important when comparing the results with photoluminescence (PL) measurements [32]. To be able to take all these factors into account, namely the large number of atoms, the atomistic description of the electronic structure, plus Coulomb correlation effects, semiempirical approaches, such as tight-binding [33][34][35] (TB) or empirical pseudopotential methods [32,36], coupled with configuration interaction (CI) schemes [32,37,38], are required.…”

Section: Introductionmentioning

confidence: 99%

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Structural, electronic, and optical properties ofm-plane InGaN/GaN quantum wells: Insights from experiment and atomistic theory

Schulz¹,

Tanner

O’Reilly

et al. 2015

Phys. Rev. B

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In this paper we present a detailed analysis of the structural, electronic, and optical properties of an m-plane (In,Ga)N/GaN quantum well structure grown by metal organic vapor phase epitaxy. The sample has been structurally characterized by x-ray diffraction, scanning transmission electron microscopy, and 3D atom probe tomography. The optical properties of the sample have been studied by photoluminescence (PL), time-resolved PL spectroscopy, and polarized PL excitation spectroscopy. The PL spectrum consisted of a very broad PL line with a high degree of optical linear polarization. To understand the optical properties we have performed atomistic tight-binding calculations, and based on our initial atom probe tomography data, the model includes the effects of strain and built-in field variations arising from random alloy fluctuations. Furthermore, we included Coulomb effects in the calculations. Our microscopic theoretical description reveals strong hole wave function localization effects due to random alloy fluctuations, resulting in strong variations in ground state energies and consequently the corresponding transition energies. This is consistent with the experimentally observed broad PL peak. Furthermore, when including Coulomb contributions in the calculations we find strong exciton localization effects which explain the form of the PL decay transients. Additionally, the theoretical results confirm the experimentally observed high degree of optical linear polarization. Overall, the theoretical data are in very good agreement with the experimental findings, highlighting the strong impact of the microscopic alloy structure on the optoelectronic properties of these systems.

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Section: Theoretical Results: Electronic Structure and Optical Prosupporting

confidence: 63%

Section: Theoretical Frameworksupporting

confidence: 63%

Section: Gs and Holementioning

confidence: 99%

Section: Theoretical Frameworkmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Structural, electronic, and optical properties ofm-plane InGaN/GaN quantum wells: Insights from experiment and atomistic theory

Schulz¹,

Tanner

O’Reilly

et al. 2015

Phys. Rev. B

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Atomistic analysis of the electronic structure of m‐plane InGaN/GaN quantum wells: Carrier localization effects in ground and excited states due to random alloy fluctuations

Tanner

Miguel

O’Reilly

et al. 2015

Physica Status Solidi (b)

Self Cite

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We present a detailed atomistic analysis of the electronic properties of m‐plane InGaN/GaN quantum wells. The tight‐binding model used treats realistically sized systems atomistically and accounts for compositional and structural inhomogeneities. Local variation in strain and built‐in potential arising from random alloy fluctuations are explicitly included in the model. Many energy states of the supercells considered are calculated in order to determine the impact of the alloy fluctuations on the electronic structure of the system under investigation. We find that while the electrons are relatively insensitive to the local indium environment, the hole states are highly sensitive to it and are subject to very strong localization effects. These effects persist several states into the valence band. This strong localization of the hole states leads to a very broad distribution of ground state energies in different random configurations. Furthermore, we see that the localization leads to poor overlap between different hole states resulting in a reduced probability of transfer of carriers between different states. This feature should play an important role for transport properties in m‐plane InGaN/GaN QWs.

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Impact of Boron Atom Clustering on the Electronic Structure of (B,In)N Alloys

Nies,

Schulz

2024

Physica Status Solidi (b)

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Tailoring the electronic and optical properties of nitride‐based alloys for optoelectronic device applications in the ultraviolet and red spectral range has attracted significant attention in recent years. Adding boron nitride (BN) to indium gallium nitride (In,Ga)N alloys can help to control the lattice mismatch between (In,Ga)N and GaN and may thus allow to reduce strain‐related defect formation. However, understanding of the impact of BN on the electronic properties of III‐N alloys, in particular the influence of experimentally observed boron atom clustering, is sparse. This work presents first‐principles calculations investigating the electronic properties of highly mismatched (B,In)N alloys with boron contents between 2% and 7%. Special attention is paid to the impact of the alloy microstructure. While the results show that the lattice constants of such alloys largely agree with lattice constants determined from a Vegard approximation, the electronic structure strongly depends on the local boron atom configuration. For instance, if boron atoms are dispersed throughout the structure and are not sharing nitrogen atoms, the band gap of (B,In)N alloys is largely unaffected and stays close to the gap of pristine InN. However, in the case of boron atom clustering, i.e., when boron atoms are sharing nitrogen atoms, the band gap can be strongly reduced, often leading to a metallic state in (B,In)N alloys. These strong band gap reductions are mainly driven by carrier localization effects in the valence band. Our calculations thus show that the electronic structure of (B,In)N alloys strongly depends on the alloy microstructure and that boron atom clustering plays an important role in understanding the electronic and optical properties of these emerging materials.

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Atomistic analysis of the impact of alloy and well-width fluctuations on the electronic and optical properties of InGaN/GaN quantum wells

Cited by 119 publications

References 59 publications

Structural, electronic, and optical properties ofm-plane InGaN/GaN quantum wells: Insights from experiment and atomistic theory

Structural, electronic, and optical properties ofm-plane InGaN/GaN quantum wells: Insights from experiment and atomistic theory

Atomistic analysis of the electronic structure of m‐plane InGaN/GaN quantum wells: Carrier localization effects in ground and excited states due to random alloy fluctuations

Impact of Boron Atom Clustering on the Electronic Structure of (B,In)N Alloys

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