Comprehensive study on initial thermal oxidation of GaN(0001) surface and subsequent oxide growth in dry oxygen ambient

Yamada, Takahiro; Ito, Joyo; Asahara, Ryohei; Watanabe, Kenta; Nozaki, Mitsuhiro; Nakazawa, Shozo; Anda, Yoshiharu; Ishida, M.; Ueda, T.; Yoshigoe, Akitaka; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji

doi:10.1063/1.4974458

Cited by 69 publications

(68 citation statements)

References 34 publications

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“…The shell thickness increases with the time and the temperature. This behavior is similar to the one observed for oxidized GaN or AlN films [50][51][52][53][54]. For the lower temperature (850 • C), two different oxidation processes can be distinguished: an initial rapid oxide-shell growth, followed by a second stage of reduced but continuous oxide growth (after about 15-20 min of oxidation).…”

Section: Ga 2 O 3 -Shell Thickness Evolution and Formationsupporting

confidence: 80%

GaN/Ga2O3 Core/Shell Nanowires Growth: Towards High Response Gas Sensors

et al. 2019

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The development of sensors working in a large range of temperature is of crucial importance in areas such as monitoring of industrial processes or personal tracking using smart objects. Devices integrating GaN/Ga2O3 core/shell nanowires (NWs) are a promising solution for monitoring carbon monoxide (CO). Because the performances of sensors primarily depend on the material properties composing the active layer of the device, it is essential to control them and achieve material synthesis in the first time. In this work, we investigate the synthesis of GaN/Ga2O3 core-shell NWs with a special focus on the formation of the shell. The GaN NWs grown by plasma-assisted molecular beam epitaxy, are post-treated following thermal oxidation to form a Ga2O3-shell surrounding the GaN-core. We establish that the shell thickness can be modulated from 1 to 14 nm by changing the oxidation conditions and follows classical oxidation process: A first rapid oxide-shell growth, followed by a reduced but continuous oxide growth. We also discuss the impact of the atmosphere on the oxidation growth rate. By combining XRD-STEM and EDX analyses, we demonstrate that the oxide-shell is crystalline, presents the β-Ga2O3 phase, and is synthesized in an epitaxial relationship with the GaN-core.

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Section: Ga 2 O 3 -Shell Thickness Evolution and Formationsupporting

confidence: 80%

GaN/Ga2O3 Core/Shell Nanowires Growth: Towards High Response Gas Sensors

et al. 2019

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“…This result demonstrates that the oxidation rate was faster with higher temperature. These results are similar to ones reported in [49][50][51][52]. The curve corresponding to the oxidation temperature of 850°C in figure 2c shows that the diameter expansion (or the increase of the oxidation rate) becomes slower with time.…”

Section: Ga2o3 Shell Thickness Evolutionsupporting

confidence: 89%

GaN/Ga<sub>2</sub>O<sub>3</sub> Core/Shell Nanowires Growth: Nanostructures for Future CO-Sensors Developments

Bui¹,

Largeau²,

Morassi³

et al. 2019

Preprint

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The development of sensors for monitoring Carbon Monoxide (CO) in a large range of temperature is of crucial importance in areas as monitoring of industrial processes or personal tracking using smart objects. Devices integrating GaN/Ga2O3 core/shell nanowires (NWs) is a promising solution allowing combining the high sensitivity of the electronic properties to the states of GaN-core surface; and the high sensitivity to CO of Ga2O3-shell. Because the performances of sensors primarily depend on the material properties composing the active layer of the device, it is essential to control these properties and in first time its synthesis. In this work, we investigate the synthesis of GaN/Ga2O3 core-shell NWs with a special focus on the formation of the shell. The GaN NWs grown by Plasma-assisted molecular beam epitaxy, are post-treated following thermal oxidation to form Ga2O3-shell surrounding the GaN-core. We establish that the Ga2O3-shell thickness can be modulated from 1 up to 14 nm by changing the oxidation conditions, and follows the diffuse-controlled reaction. By combining XRD-STEM and EDX analysis, we also demonstrate that the oxide shell formed by thermal oxidation is crystalline and presents the β-Ga2O3 crystalline phase, and is synthesized in epitaxial relationship with the GaN-core.

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“…Under the sufficient time and driving force provided by high temperature, the polycrystalline Ga 2 O 3 shells are further annealed and tiny Ga 2 O 3 grains further migrate and accumulate to produce large crystalline grains (described in detail in ref. ). Finally, the oxidized nanowires convert from the core‐shell structure to the “polycrystalline‐like” one.…”

Section: Resultsmentioning

confidence: 97%

Broadband Ultraviolet Photodetector Based on Vertical Ga₂O₃/GaN Nanowire Array with High Responsivity

Zhang

Ding

et al. 2019

Advanced Optical Materials

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attracted significant attention, which has a vast and growing number of military and civilian applications such as fire detection, missile interception, ozone hole monitoring, bioaerosol detection, astronomical imaging, and so on. [1][2][3] As the continuous improvement of devices integration, environment complexity, and interference technology, BUV photodetectors can effectively reduce false alarm rates in early warning, searching, and tracking systems, to improve the accuracy and versatility of detection systems in various situations. Many heterojunction structures based on wide-band-gap semiconductors have been reported to achieve the BUV photodetectors such as AlGaN/GaN, MgZnO/ZnO, and Ga 2 O 3 /GaN heterojunction. [4][5][6][7][8][9][10] However, AlGaN/GaN heterojunction has a high conduction band discontinuity which impedes the flow of photogenerated electrons and reduces the performance of photodetectors. [11] And high Mg-content MgZnO with high crystal quality is difficult to achieve by epitaxial growth due to the phase segregation in single wurtzite phase MgZnO. [12] β-Ga 2 O 3 with an ultrawide bandage of 4.9 eV is considered as a promising candidate for UV detection. [13,14] It has great thermal and chemical stability, determining its possibility of working at high temperatures and strong radiations. Moreover, there is a small lattice mismatch and a low conduction band offset at the interface between Ga 2 O 3 and GaN. These characteristics mean that Ga 2 O 3 /GaN heterojunction could be a potential for BUV photodetectors. Kalra et al. [6] demonstrated epitaxial β-Ga 2 O 3 /GaN-based vertical metal-heterojunctionmetal multiband UV photodetectors with the responsivity (R) of 3.7 A W −1 at 256 and 365 nm. For saving energy and broadening the application prospects of UV photodetectors, Guo et al. [15] fabricated a super-high-performance self-powered UV photodetector based on the GaN/Sn:Ga 2 O 3 p-n junction generated by depositing a Sn-doped n-type Ga 2 O 3 thin film onto a p-type GaN thick film. The responsivity at 254 nm reached up to 3.05 A W −1 without consuming external power. Lin et al. [16] used graphene as the transparent conductive layer to form graphene/β-Ga 2 O 3 /GaN heterojunction. With the help of largearea transparent electrode, a typical "sandwich" structure UV photodetector with low dark current density (1.25 × 10 −8 A cm −2 ) and high sensitivity (12.8 A W −1 ) was successfully assembled. Broadband ultraviolet (BUV) photodetectors responding to the multiband spectrum can effectively reduce false alarm rates and improve the accuracy and versatility of detection systems in various situations. A high-responsivityBUV photodetector based on vertical Ga 2 O 3 /GaN nanowire array is proposed and demonstrated. Ga 2 O 3 /GaN nanowires are obtained by partially thermally oxidizing GaN nanowires grown by molecular beam epitaxy and used to combine with a monolayer graphene film to form graphene/Ga 2 O 3 /GaN heterojunction. Moreover, the oxidation mechanism of GaN nanowires is further investigated by ...

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Comprehensive study on initial thermal oxidation of GaN(0001) surface and subsequent oxide growth in dry oxygen ambient

Cited by 69 publications

References 34 publications

GaN/Ga2O3 Core/Shell Nanowires Growth: Towards High Response Gas Sensors

GaN/Ga2O3 Core/Shell Nanowires Growth: Towards High Response Gas Sensors

GaN/Ga<sub>2</sub>O<sub>3</sub> Core/Shell Nanowires Growth: Nanostructures for Future CO-Sensors Developments

Broadband Ultraviolet Photodetector Based on Vertical Ga₂O₃/GaN Nanowire Array with High Responsivity

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Comprehensive study on initial thermal oxidation of GaN(0001) surface and subsequent oxide growth in dry oxygen ambient

Cited by 69 publications

References 34 publications

GaN/Ga2O3 Core/Shell Nanowires Growth: Towards High Response Gas Sensors

GaN/Ga2O3 Core/Shell Nanowires Growth: Towards High Response Gas Sensors

GaN/Ga<sub>2</sub>O<sub>3</sub> Core/Shell Nanowires Growth: Nanostructures for Future CO-Sensors Developments

Broadband Ultraviolet Photodetector Based on Vertical Ga2O3/GaN Nanowire Array with High Responsivity

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Broadband Ultraviolet Photodetector Based on Vertical Ga₂O₃/GaN Nanowire Array with High Responsivity