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13 pages, 4326 KiB

Open AccessEditor’s ChoiceArticle

Controlled Crystallinity of a Sn-Doped α-Ga₂O₃ Epilayer Using Rapidly Annealed Double Buffer Layers

by Kyoung-Ho Kim, Yun-Ji Shin, Seong-Min Jeong, Heesoo Lee and Si-Young Bae

Nanomaterials 2024, 14(2), 178; https://doi.org/10.3390/nano14020178 - 12 Jan 2024

Cited by 2 | Viewed by 1867

Double buffer layers composed of (Al_xGa_1−x)₂O₃/Ga₂O₃ structures were employed to grow a Sn-doped α-Ga₂O₃ epitaxial thin film on a sapphire substrate using mist chemical vapor deposition. The insertion of double buffer layers improved the crystal quality of the upper-grown Sn-doped α-Ga₂O₃ thin films by blocking dislocation generated by the substrates. Rapid thermal annealing was conducted for the double buffer layers at phase transition temperatures of 700–800 °C. The slight mixing of κ and β phases further improved the crystallinity of the grown Sn-Ga₂O₃ thin film through local lateral overgrowth. The electron mobility of the Sn-Ga₂O₃ thin films was also significantly improved due to the smoothened interface and the diffusion of Al. Therefore, rapid thermal annealing with the double buffer layer proved advantageous in achieving strong electrical properties for Ga₂O₃ semiconductor devices within a shorter processing time. Full article

(This article belongs to the Special Issue Advances in Wide-Bandgap Semiconductor Nanomaterials)

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10 pages, 3676 KiB

Open AccessArticle

One-Step Preparation of Si-Doped Ultra-Long β-Ga₂O₃ Nanowires by Low-Pressure Chemical Vapor Deposition

by Minglei Tang, Guodong Wang, Songhao Wu and Yang Xiang

Crystals 2023, 13(6), 898; https://doi.org/10.3390/cryst13060898 - 31 May 2023

Cited by 5 | Viewed by 1873

Abstract

In this work, we prepared ultra-long Si-doped β-Ga₂O₃ nanowires on annealed Al₂O₃-film/Si substrate by low-pressure chemical vapor deposition (LPCVD) assisted by Au as catalyst. The length of nanowires exceeds 300 μm and diameters range from ~30 to ~100 nm in one-dimensional structures. The nanowires show good crystal quality and exhibit (201) orientation, confirmed by transmission electron microscopy and X-ray diffraction analysis. The PL spectrum obtained from these β-Ga₂O₃ nanowires has three obvious blue luminescence peaks at 398 nm (3.12 eV), 440 nm (2.82 eV), and 492 nm (2.51 eV). The electrical properties obtained from Si-doped β-Ga₂O₃ nanowires exhibit good conductivity. A metal-semiconductor-metal device is made by using Ti/Au as the electrode, and the device current reaches 200 pA at a bias voltage of 3 V. Our results show that ultra-long Si-doped β-Ga₂O₃ nanowires can be grown directly on the surface of Al₂O₃-film/Si substrates. These nanowires have a very high length-diameter ratio and good electrical properties. A possible mechanism for Si doping is also presented. Full article

(This article belongs to the Special Issue Wide Bandgap Semiconductor Electronics and Optoelectronics)

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11 pages, 1702 KiB

Open AccessArticle

Crucial Role of Oxygen Vacancies in Scintillation and Optical Properties of Undoped and Al-Doped β-Ga₂O₃ Single Crystals

by Ruifeng Tian, Mingyan Pan, Qinglin Sai, Lu Zhang, Hongji Qi and Hany Fathy Mohamed

Crystals 2022, 12(3), 429; https://doi.org/10.3390/cryst12030429 - 19 Mar 2022

Cited by 20 | Viewed by 4092

Abstract

In this paper, the effects of oxygen vacancy and gallium vacancy on the optical and scintillation properties of undoped β-Ga₂O₃ crystal and 2.5 mol % Al doped gallium oxide were investigated. For the undoped β-Ga₂O₃, the transmittance is improved after annealing in oxygen or nitrogen atmosphere. After the introduction of Al element, the absorption cutoff appears slightly blue shift, and the band gap increases. For the undoped as-grown β-Ga₂O₃ single crystals, the decay time consists of a fast component (τ₁) of the order of nanoseconds, and two slow components (τ₂, τ₃) of tens to hundreds of nanoseconds. The contribution of the fast decay time component in the decay times is 2.78%. While for Al-doped β-Ga₂O₃, the faster (τ₁) time is 2.33 ns for the as-grown one, and the contribution is 68.02%. However, the pulse height spectrum shows that the introduction of 2.5 mol % Al will reduce the light yield of the β-Ga₂O₃ crystal. Full article

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20 pages, 9694 KiB

Open AccessArticle

P-type Inversion at the Surface of β-Ga₂O₃ Epitaxial Layer Modified with Au Nanoparticles

by Maciej Krawczyk, Ryszard Korbutowicz, Rafał Szukiewicz, Patrycja Suchorska-Woźniak, Maciej Kuchowicz and Helena Teterycz

Sensors 2022, 22(3), 932; https://doi.org/10.3390/s22030932 - 25 Jan 2022

Cited by 7 | Viewed by 3506

Abstract

The electric properties and chemical and thermal stability of gallium oxide β-Ga₂O₃ make it a promising material for a wide variety of electronic devices, including chemiresistive gas sensors. However, p-type doping of β-Ga₂O₃ still remains a challenge. A β-Ga₂O₃ epitaxial layer with a highly developed surface was synthesized on gold electrodes on a Al₂O₃ substrate via a Halide Vapor Phase Epitaxy (HVPE) method. The epitaxial layer was impregnated with an aqueous colloidal solution of gold nanoparticles with an average diameter of Au nanoparticle less than 5 nm. Electrical impedance of the layer was measured before and after modification with the Au nanoparticles in an ambient atmosphere, in dry nitrogen, and in air containing dimethyl sulfide C₂H₆S (DMS). After the impregnation of the β-Ga₂O₃ epitaxial layer with Au nanoparticles, its conductance increased, and its electric response to air containing DMS had been inversed. The introduction of Au nanoparticles at the surface of the metal oxide was responsible for the formation of an internal depleted region and p-type conductivity at the surface. Full article

(This article belongs to the Special Issue Thin Film Gas Sensors)

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26 pages, 8703 KiB

Open AccessReview

Epitaxy of III-Nitrides on β-Ga₂O₃ and Its Vertical Structure LEDs

by Weijiang Li, Xiang Zhang, Ruilin Meng, Jianchang Yan, Junxi Wang, Jinmin Li and Tongbo Wei

Micromachines 2019, 10(5), 322; https://doi.org/10.3390/mi10050322 - 13 May 2019

Cited by 32 | Viewed by 7015

Abstract

β-Ga₂O₃, characterized with high n-type conductivity, little lattice mismatch with III-Nitrides, high transparency (>80%) in blue, and UVA (400–320 nm) as well as UVB (320–280 nm) regions, has great potential as the substrate for vertical structure blue and especially ultra violet LEDs (light emitting diodes). Large efforts have been made to improve the quality of III-Nitrides epilayers on β-Ga₂O₃. Furthermore, the fabrication of vertical blue LEDs has been preliminarily realized with the best result that output power reaches to 4.82 W (under a current of 10 A) and internal quantum efficiency (IQE) exceeds 78% by different groups, respectively, while there is nearly no demonstration of UV-LEDs on β-Ga₂O₃. In this review, with the perspective from materials to devices, we first describe the basic properties, growth method, as well as doping of β-Ga₂O₃, then introduce in detail the progress in growth of GaN on (1 0 0) and (−2 0 1) β-Ga₂O₃, followed by the epitaxy of AlGaN on gallium oxide. Finally, the advances in fabrication and performance of vertical structure LED (VLED) are presented. Full article

(This article belongs to the Special Issue Nanostructured Light-Emitters)

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