Ultraviolet optoelectronic devices based on AIGaN alloys grown by molecular beam epitaxy

Moustakas, T. D.

doi:10.1557/mrc.2016.26

Cited by 43 publications

(23 citation statements)

References 144 publications

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“…In this system, superlattices emerge in the [111] direction. 99 For this particular system, the ordering was attributed to surface phenomena rather than bulk thermodynamics. 100,101 In the case of III-nitrides, Northrup et al 102 investigated the system of InGaN and they reported that the ordering in this system is driven kinetically by surface phenomena.…”

Section: Discussionmentioning

confidence: 95%

First-principles study of the impact of the atomic configuration on the electronic properties of AlxGa1−xN alloys

2019

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We employ first principles calculations in the formalism of standard and hybrid density functional theory to study the electronic and structural properties of wurtzite AlxGa1−xN alloys. We address the discrepancies observed in literature regarding essential electronic properties of these alloys and we investigate the dependence of these properties on the atomic ordering and composition. We show that the bowing parameter is significantly affected by the atomic ordering, ranging from zero to strong downward bowing. The effects of atomic ordering of the alloys on their band offset with respect to the pure phases is also investigated. Finally, using the effective band structure approach, we study the electronic band structure of the random alloys.

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Section: Discussionmentioning

confidence: 95%

First-principles study of the impact of the atomic configuration on the electronic properties of AlxGa1−xN alloys

2019

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“…Conventional wurtzite (WZ) III‐nitrides materials have attracted great attention owing to their excellent structural and electronic properties for device applications. Especially, Al x Ga 1− x N alloys with tunable direct bandgap which can cover a wide ultraviolet (UV) spectral region (200–360 nm), have driven intense research in the development of UV devices recently .…”

Section: Introductionmentioning

confidence: 99%

Structural and electronic properties of wurtzite B_xAl_1–xN from first‐principles calculations

Zhang

2017

Physica Status Solidi (b)

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The structural and electronic properties of wurtzite BxAl1−xN (0 ≤ x ≤ 1) are studied using density functional theory. The change of lattice parameters with increased B composition shows small bowing parameters and thus slightly nonlinearity. The bandgap exhibits strong dependence on the B composition, where transition from direct to indirect bandgap occurs at a relatively low B composition (x ∼ 0.12) is observed, above which the bandgap of BxAl1−xN maintained indirect, thus desirable for low‐absorption optical structures. The Γv‐Ac and Γv‐Kc indirect bandgaps are dominant at lower and higher B compositions, respectively. Density of states (DOS) of the valence band is susceptible to the B incorporation. Strong hybridization of Al, B, and N in p‐states leads to high DOS near the valence band maximum. The hybridization of Al and B in s‐states at lower B compositions and p‐states of B at higher B compositions give rise to high DOS near lower end of the upper valence band. Charge density analysis reveals the B‐N chemical bond is more covalent than the Al‐N bond. This will lead to more covalent crystal with increasing B composition. Dramatic change of the heavy hole effective mass is found due to significant curvature increase of the band by minor B incorporation.

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“…However, AlGaN-based DUV LEDs still suffer from a series of challenges. Firstly, the performance of DUV LED is limited by low internal quantum efficiency (IQE) which is attributed to the high threading dislocation density (TDD) of AlGaN epilayers [3], [4]. Secondly, because of a higher electron mobility than that of holes' [5], [6] and the difficulty of p-type doping compared with the n-type, the hole density is much lower than the electron density in the QWs [7], leading to a relatively large leakage current and low radiative recombination, especially in the AlGaN based DUV LED with high Al composition (Al% > 50%) [8].…”

Section: Introductionmentioning

confidence: 99%

Enhanced Performance of an AlGaN-Based Deep-Ultraviolet LED Having Graded Quantum Well Structure

Chen

Ren

et al. 2019

IEEE Photonics J.

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AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) suffer from severe quantum confined Stark effect (QCSE) due to the strong polarization field in the quantum wells (QWs) grown on c-plane substrates. In this paper, we propose a novel DUV LED structure embedded with graded QWs in which the Al composition was linearly changed to screen the QCSE. A significant increase of the internal quantum efficiency and thus an enhancement of the light output power by nearly 67% can be achieved, attributing to the improvement of the electron-hole wave function overlap (Г e−hh) to 58.6% in the Increased-Al-composition graded QWs, as compared to the QW without grading (Г e−hh = 40.4%) and reverse grading (Г e−hh = 33.6%). Further investigations show that the grading profile of the Al composition in the QWs, including either linearly increases or decreases along the growth direction and the thickness of graded QWs, determine the polarization electrical field in the QWs and as a result, significantly affecting the performance of the devices. In the end, a careful optimization of the graded QWs is called. The proposed structure with such unique graded QWs provides us an effective solution to suppress the QCSE effect in the pursuit of high-performance DUV emitters.

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Ultraviolet optoelectronic devices based on AIGaN alloys grown by molecular beam epitaxy

Cited by 43 publications

References 144 publications

First-principles study of the impact of the atomic configuration on the electronic properties of AlxGa1−xN alloys

First-principles study of the impact of the atomic configuration on the electronic properties of AlxGa1−xN alloys

Structural and electronic properties of wurtzite B_xAl_1–xN from first‐principles calculations

Enhanced Performance of an AlGaN-Based Deep-Ultraviolet LED Having Graded Quantum Well Structure

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Ultraviolet optoelectronic devices based on AIGaN alloys grown by molecular beam epitaxy

Cited by 43 publications

References 144 publications

First-principles study of the impact of the atomic configuration on the electronic properties of AlxGa1−xN alloys

First-principles study of the impact of the atomic configuration on the electronic properties of AlxGa1−xN alloys

Structural and electronic properties of wurtzite BxAl1–xN from first‐principles calculations

Enhanced Performance of an AlGaN-Based Deep-Ultraviolet LED Having Graded Quantum Well Structure

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Structural and electronic properties of wurtzite B_xAl_1–xN from first‐principles calculations