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11 pages, 4665 KB

Open AccessArticle

High-Quality GaP(111) Grown by Gas-Source MBE for Photonic Crystals and Advanced Nonlinear Optical Applications

by Karine Hestroffer, Kelley Rivoire, Jelena Vučković and Fariba Hatami

Nanomaterials 2025, 15(8), 619; https://doi.org/10.3390/nano15080619 - 18 Apr 2025

Viewed by 630

The precise fabrication of semiconductor-based photonic crystals with tailored optical properties is critical for advancing photonic devices. GaP(111) is a material of particular interest due to its high refractive index, wide optical bandgap, and pronounced optical anisotropy, offering unique opportunities for photonic applications. Its near-lattice matching with silicon substrates further facilitates integration with existing silicon-based technologies. In this study, we present the growth of high-quality GaP(111) thin films using gas-source molecular-beam epitaxy (GSMBE), achieving atomically smooth terraces for the homo-epitaxy of GaP(111). We demonstrate the fabrication of photonic crystal cavities from GaP(111), employing AlGaP(111) as a sacrificial layer, and achieve a quality factor of 1200 for the cavity mode with resonance around 1500 nm. This work highlights the potential of GaP(111) for advanced photonic architectures, particularly in applications requiring strong light confinement and nonlinear optical processes, such as second-harmonic and sum-frequency generation. Full article

(This article belongs to the Special Issue Light-Matter Interaction in Nano Systems: Fundamentals and Applications)

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7 pages, 3998 KB

Open AccessArticle

Development and Characterization of an Advanced Voltage-Controllable Capacitor Based on AlInGaN/GaN-Si (111) Epitaxy

by He Guan and Guiyu Shen

Coatings 2024, 14(10), 1254; https://doi.org/10.3390/coatings14101254 - 1 Oct 2024

Cited by 1 | Viewed by 922

Abstract

The AlInGaN/GaN heterojunction epitaxy material with high cutoff frequency and saturated power density has become a very popular candidate for millimeter wave applications in next-generation mobile communication. In this study, an advanced voltage-controllable capacitor based on the AlInGaN/GaN-Si (111) epitaxy was proposed by employing a bi-directional series MIS capacitor structure. The capacitor was fabricated by using a pad area of 40 μm × 40 μm, with a 1 μm distance between the positive and negative electrodes. The test results show that the capacitance is turned on with a saturation capacitance density and a maximum leakage current density of 0.30 fF/μm² of 0.37 pA/μm², respectively, for the control voltage from −6.5 V to 6 V. In particular, in the proposed design method, the saturation capacitance required for the practical application can be obtained by simply adjusting the capacitance area. The capacitor showcases characteristics of rapid turn-on and turn-off responses coupled with low loss, underscoring its promising prospects for deployment in RF switching applications. Full article

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10 pages, 4010 KB

Open AccessArticle

Study on P-AlGaAs/Al/Au Ohmic Contact Characteristics for Improving Optoelectronic Response of Infrared Light-Emitting Device

by Hyung-Joo Lee, Jae-Sam Shim, Jin-Young Park, Lee-Ku Kwac and Chang-Ho Seo

Micromachines 2023, 14(5), 1053; https://doi.org/10.3390/mi14051053 - 16 May 2023

Cited by 1 | Viewed by 2568

Abstract

The Al/Au alloy was investigated to improve the ohmic characteristic and light efficiency of reflective infrared light-emitting diodes (IR-LEDs). The Al/Au alloy, which was fabricated by combining 10% aluminum and 90% gold, led to considerably improved conductivity on the top layer of p-AlGaAs of the reflective IR-LEDs. In the wafer bond process required for fabricating the reflective IR-LED, the Al/Au alloy, which has filled the hole patterns in Si₃N₄ film, was used for improving the reflectivity of the Ag reflector and was bonded directly to the top layer of p-AlGaAs on the epitaxial wafer. Based on current-voltage measurements, it was found that the Al/Au alloyed material has a distinct ohmic characteristic pertaining to the p-AlGaAs layer compared with those of the Au/Be alloy material. Therefore, the Al/Au alloy may constitute one of the favored approaches for overcoming the insulative reflective structures of reflective IR-LEDs. For a current density of 200 mA, a lower forward voltage (1.56 V) was observed from the wafer bond IR-LED chip made with the Al/Au alloy; this voltage was remarkably lower in value than that of the conventional chip made with the Au/Be metal (2.29 V). A higher output power (182 mW) was observed from the reflective IR-LEDs made with the Al/Au alloy, thus displaying an increase of 64% compared with those made with the Au/Be alloy (111 mW). Full article

(This article belongs to the Special Issue III–V Compound Semiconductors and Devices)

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11 pages, 3413 KB

Open AccessEditor’s ChoiceArticle

Studies of Defect Structure in Epitaxial AlN/GaN Films Grown on (111) 3C-SiC

by Andreea Bianca Serban, Vladimir Lucian Ene, Doru Dinescu, Iulia Zai, Nikolay Djourelov, Bogdan Stefan Vasile and Victor Leca

Nanomaterials 2021, 11(5), 1299; https://doi.org/10.3390/nano11051299 - 14 May 2021

Cited by 3 | Viewed by 3328

Abstract

Several aspects such as the growth relation between the layers of the GaN/AlN/SiC heterostructure, the consistency of the interfaces, and elemental diffusion are achieved by High Resolution Transmission Electron Microscopy (HR-TEM). In addition, the dislocation densities together with the defect correlation lengths are investigated via High-Resolution X-ray Diffraction (HR-XRD) and the characteristic positron diffusion length is achieved by Doppler Broadening Spectroscopy (DBS). Moreover, a comparative analysis with our previous work (i.e., GaN/AlN/Si and GaN/AlN/Al₂O₃) has been carried out. Within the epitaxial GaN layer defined by the relationship

F \bar{4} 3 m

(111) 3C-SiC ||

P 63 m c

(0002) AlN ||

P 63 m c

(0002) GaN, the total dislocation density has been assessed as being 1.47 × 10¹⁰ cm⁻². Compared with previously investigated heterostructures (on Si and Al₂O₃ substrates), the obtained dislocation correlation lengths (L^e = 171 nm and L^s =288 nm) and the mean distance between two dislocations (r_d = 82 nm) are higher. This reveals an improved crystal quality of the GaN with SiC as a growth template. In addition, the DBS measurements upheld the aforementioned results with a higher effective positron diffusion length

L_{eff}^{GaN 2}

= 75 ± 20 nm for the GaN layer. Full article

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9 pages, 1734 KB

Open AccessArticle

Simple Model for Corrugation in Surface Alloys Based on First-Principles Calculations

by Monika Nur, Naoya Yamaguchi and Fumiyuki Ishii

Materials 2020, 13(19), 4444; https://doi.org/10.3390/ma13194444 - 7 Oct 2020

Cited by 5 | Viewed by 3020

Abstract

The structural stability of M/Ag(111)–

(\sqrt{3} \times \sqrt{3}) R 30 °

surface alloys is systematically investigated by using first-principles calculations, where M is a member of group III (B, Al, Ga, In, Tl), IV (C, Si, Ge, Sn, Pb), and V [...] Read more.

The structural stability of M/Ag(111)–

(\sqrt{3} \times \sqrt{3}) R 30 °

surface alloys is systematically investigated by using first-principles calculations, where M is a member of group III (B, Al, Ga, In, Tl), IV (C, Si, Ge, Sn, Pb), and V (N, P, As, Sb, Bi) elements. We focus on the corrugation parameter d which is determined by the height of the M atom from the Ag atom in the plane of the top-most atom, and the relation between atomic radii and corrugations in M/Ag(111) is obtained. The tendencies of the corrugation parameter d can be understood by using a simple hard spherical atomic model. We introduce a new type of atomic radii determined by the corrugation in surface alloys, surface alloy atomic radii, which can be useful for rapid predictions of the structures of surface alloys, not only for M/Ag (111)–

(\sqrt{3} \times \sqrt{3}) R 30 °

systems but also for other surface alloys. Full article

(This article belongs to the Section Materials Physics)

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10 pages, 4582 KB

Open AccessArticle

Direct Growth of AlGaN Nanorod LEDs on Graphene-Covered Si

by Fang Ren, Yue Yin, Yunyu Wang, Zhiqiang Liu, Meng Liang, Haiyan Ou, Jinping Ao, Tongbo Wei, Jianchang Yan, Guodong Yuan, Xiaoyan Yi, Junxi Wang, Jinmin Li, Dheeraj Dasa and Helge Weman

Materials 2018, 11(12), 2372; https://doi.org/10.3390/ma11122372 - 26 Nov 2018

Cited by 18 | Viewed by 6132

Abstract

High density of defects and stress owing to the lattice and thermal mismatch between nitride materials and heterogeneous substrates have always been important problems and limit the development of nitride materials. In this paper, AlGaN light-emitting diodes (LEDs) were grown directly on a single-layer graphene-covered Si (111) substrate by metal organic chemical vapor deposition (MOCVD) without a metal catalyst. The nanorods was nucleated by AlGaN nucleation islands with a 35% Al composition, and included n-AlGaN, 6 period of AlGaN multiple quantum wells (MQWs), and p-AlGaN. Scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) showed that the nanorods were vertically aligned and had an accordant orientation along the [0001] direction. The structure of AlGaN nanorod LEDs was investigated by scanning transmission electron microscopy (STEM). Raman measurements of graphene before and after MOCVD growth revealed the graphene could withstand the high temperature and ammonia atmosphere in MOCVD. Photoluminescence (PL) and cathodoluminescence (CL) characterized an emission at ~325 nm and demonstrated the low defects density in AlGaN nanorod LEDs. Full article

(This article belongs to the Special Issue Graphene and other Two-dimensional Materials in Nanoelectronics and Optoelectronics)

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18 pages, 599 KB

Open AccessArticle

Effects of Alloying Atoms on Antiphase Boundary Energy and Yield Stress Anomaly of L1₂ Intermetallics: First-Principles Study

by Xiaojun Gao, Jianwei Wang, Xiaozhi Wu, Rui Wang and Zhihong Jia

Crystals 2018, 8(2), 96; https://doi.org/10.3390/cryst8020096 - 12 Feb 2018

Cited by 10 | Viewed by 5870

Abstract

The antiphase boundary energies of {111} and {010} planes in L1

_{2}

intermetallics (Ni

_{3}

Ge, Ni

_{3}

Si, Al

_{3}

Sc, Ni

_{3}

Al, Ni

_{3}

Ga and Al

_{3}

Ti) under different pressure are presented using first-principle methods. The yield stress [...] Read more.

The antiphase boundary energies of {111} and {010} planes in L1

_{2}

intermetallics (Ni

_{3}

Ge, Ni

_{3}

Si, Al

_{3}

Sc, Ni

_{3}

Al, Ni

_{3}

Ga and Al

_{3}

Ti) under different pressure are presented using first-principle methods. The yield stress anomaly is predicted by the energy criterion p-factor based on the anisotropy of antiphase boundary energies and elasticity. These L1

_{2}

intermetallics exhibit anomalous yield stress behavior except Al

_{3}

Sc. It is found that pressure cannot introduce the transition between anomalous and normal behavior. In order to investigate the transition, Al

_{3}

Sc, Ni

_{3}

Si and Ni

_{3}

Ge with substituting atoms are investigated in detail due to p-factors of them are close to the critical value

p_{c} = \sqrt{3}

. Al

_{3}

Sc can change to anomalous when Sc atoms in {010} planes are substituted by Ti with plane concentration 25%. When Li substitutes Al in {111} planes, anomalous Al

_{3}

Sc will change to normal. Ni

_{3}

Si and Ni

_{3}

Ge can exhibit normal yield stress behavior when Ge and Si in {111} planes are substituted by alloying atoms with plane concentrations 12.5% and 25%. When Ga and Al substitute in {010} planes, normal Ni

_{3}

Si and Ni

_{3}

Ge will revert to anomalous behavior. Therefore, transparent transition between normal and anomalous yield stress behavior in L1

_{2}

intermetallics can be introduced by alloying atoms. Full article

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