β-Ga2O3作为新型宽禁带半导体材料,近年来受到了人们的广泛关注。β-Ga2O3禁带宽度可达4. 7 e V,相比于第三代半导体SiC和Ga N,具有禁带宽度更大、击穿场强更高、Baliga品质因子更大、吸收截止边更短、生长成本更低的优点,有望成为高...β-Ga2O3作为新型宽禁带半导体材料,近年来受到了人们的广泛关注。β-Ga2O3禁带宽度可达4. 7 e V,相比于第三代半导体SiC和Ga N,具有禁带宽度更大、击穿场强更高、Baliga品质因子更大、吸收截止边更短、生长成本更低的优点,有望成为高压、大功率、低损耗功率器件和深紫外光电子器件的优选材料。此外,β-Ga2O3单晶可以通过熔体法生长,材料制备成本相对较低,有利于大规模应用。重点介绍了β-Ga2O3单晶的生长及工艺优化,然后对晶体加工、性能表征、光电探测及功率器件应用等方面进行了讨论,并展望了β-Ga2O3晶体未来的发展方向。展开更多
Perfluorooctanoic acid （PFOA） is a new-found hazardous persistent organic pollutant, and it is resistant to decomposition by hydroxyl radical （HO.） due to its stable chemical structure and the high electronegativi...Perfluorooctanoic acid （PFOA） is a new-found hazardous persistent organic pollutant, and it is resistant to decomposition by hydroxyl radical （HO.） due to its stable chemical structure and the high electronegativity of fluorine. Photocatalytic reduction of PFOA with β-Ga2O3 in anoxic aqueous solution was investigated for the first time, and the results showed that the photoinduced electron （ecb） coming from the β-Ga2O3 conduction band was the major degradation substance for PFOA, and shorter-chain perfluorinated carboxylic acids （PFCAs, CnF2n＋1COOH, 1 ≤ n ≤ 6） were the dominant products. Furthermore, the concentration of F- was measured by the IC technique and defluorination efficiency was calculated. After 3 hr, the photocatalytic degradation efficiency was 98.8% and defluorination efficiency was 31.6% in the presence of thiosulfate and bubbling N2. The degradation reaction followed first-order kinetics （k = 0.0239 min-1, t1/2 = 0.48 hr）. PFCAs （CnF2n＋xCOOH, 1 ≤ n≤ 7） were detected and measured by LC-MS and LC-MS/MS methods. It was deduced that the probable photocatalytic degradation mechanism involves ec-b attacking the carboxyl of CnF2n＋1COOH, resulting in decarboxylation and the generation of CnFzn＋1. The produced CnF2n＋1 reacted with H2O, forming CnF2n＋1OH, then CnF2n＋1OH underwent HF loss and hydrolysis to form CnF2,＋1COOH.展开更多
The band structure, density of states, electron density difference and optical properties of intrinsic β-Ga2O3 and N-doped β-Ga2O3 were calculated using first-principles based on density functional theory. After N d...The band structure, density of states, electron density difference and optical properties of intrinsic β-Ga2O3 and N-doped β-Ga2O3 were calculated using first-principles based on density functional theory. After N doping, the band gap decreases, shallow acceptor impurity levels are introduced over the top of the valence band and the absorption band edge is slightly red-shifted compared to that of the intrinsic one. The anisotropic optical properties are investigated by means of the complex dielectric function, which are explained by the selection rule of the band-to-band transitions. All calculation results indicate that N-doping is a very promising method to get P-type β-Ga2O3.展开更多
The electronic structure and optical properties of N-doped β-Ga2O3 and N-Zn co-doped β-Ga2O3 are investigated by the first-principles calculation. In the N-Zn co-doped β-Ga2O3 system, the lattice parameters of a, b...The electronic structure and optical properties of N-doped β-Ga2O3 and N-Zn co-doped β-Ga2O3 are investigated by the first-principles calculation. In the N-Zn co-doped β-Ga2O3 system, the lattice parameters of a, b, c, V decrease and the total energy Etot,l increases in comparison with N-doped β-Ga2O3. The calculated ionization energy of N-Zn co-doped β-Ga2O3 is smaller than that of N-doped β-Ga2O3. Two shallower acceptor impurity levels are introduced in N-Zn co-doped β-Ga2O3. Compared with N-doped β-Ga2O3, the major absorption peak is red-shifted and the impurity absorption edge is blue-shifted for N-Zn co-dopedβ-Ga2O3. The results show that the N-Zn co-doped β-Ga2O3 is found to be a better method to push p-type conductivity in β-Ga2O3.展开更多
As a wide-bandgap semiconductor(WBG), β-Ga_2O_3 is expected to be applied to power electronics and solar blind UV photodetectors. In this review, defects in β-Ga_2O_3 single crystals were summarized, including dislo...As a wide-bandgap semiconductor(WBG), β-Ga_2O_3 is expected to be applied to power electronics and solar blind UV photodetectors. In this review, defects in β-Ga_2O_3 single crystals were summarized, including dislocations, voids, twin, and small defects. Their effects on device performance were discussed. Dislocations and their surrounding regions can act as paths for the leakage current of SBD in single crystals. However, not all voids lead to leakage current. There's no strong evidence yet to show small defects affect the electrical properties. Doping impurity was definitely irrelated to the leakage current. Finally, the formation mechanism of the defects was analyzed. Most small defects were induced by mechanical damages. The screw dislocation originated from a subgrain boundary. The edge dislocation lying on a plane slightly tilted towards the(102) plane, the(101) being the possible slip plane. The voids defects like hollow nanopipes, PNPs, NSGs and line-shaped grooves may be caused by the condensation of excess oxygen vacancies, penetration of tiny bubbles or local meltback. The nucleation of twin lamellae occurred at the initial stage of "shoulder part" during the crystal growth. These results are helpful in controlling the occurrence of crystal defects and improving the device performance.展开更多
Monoclinic gallium oxide(Ga_2O_3) has been grown on(0001) sapphire(Al_2O_3) substrate by plasma-assisted molecular beam epitaxy(PA-MBE). The epitaxial relationship has been confirmed to be [010]( 2ˉ01) β-Ga_2O_3||[ ...Monoclinic gallium oxide(Ga_2O_3) has been grown on(0001) sapphire(Al_2O_3) substrate by plasma-assisted molecular beam epitaxy(PA-MBE). The epitaxial relationship has been confirmed to be [010]( 2ˉ01) β-Ga_2O_3||[ 011ˉ0](0001)Al_2O_3 via in-situ reflection high energy electron diffraction(RHEED) monitoring and ex-situ X-ray diffraction(XRD) measurement. Crystalline quality is improved and surface becomes flatter with increasing growth temperature, with a best full width at half maximum(FWHM) of XRD ω-rocking curve of( 2ˉ01) plane and root mean square(RMS) roughness of 0.68° and 2.04 nm for the sample grown at 730 °C,respectively. Room temperature cathodoluminescence measurement shows an emission at ～417 nm, which is most likely originated from recombination of donor–acceptor pair(DAP).展开更多
β-Ga2O3: Cr single crystals were grown by floating zone technique. Absorption spectra and fluorescence spectra were measured at room temperature. The values of field splitting parameter Dq and Racah parameter B were ...β-Ga2O3: Cr single crystals were grown by floating zone technique. Absorption spectra and fluorescence spectra were measured at room temperature. The values of field splitting parameter Dq and Racah parameter B were obtained by the peak values of absorption spectra. The value 10Dq/B=23.14 manifests that in β-Ga2O3 crystals Cr3+ ions are influenced by low energy crystal field. After high temperature annealing in air, the Cr3+ intrinsic emission was enhanced and the green lumines-cence disappeared. The strong and broad 691 nm emission was obtained at 420 nm excitation due to the electron transition occurred from 4T2 to 4A2. The studies manifest that the β-Ga2O3 crystals have the potential application for tunable laser.展开更多
The electronic structures and optical properties of β-Ga_2O_3 and Si-and Sn-doped β-Ga_2O_3 are studied using the GGA + U method based on density functional theory. The calculated bandgap and Ga 3d-state peak of β-...The electronic structures and optical properties of β-Ga_2O_3 and Si-and Sn-doped β-Ga_2O_3 are studied using the GGA + U method based on density functional theory. The calculated bandgap and Ga 3d-state peak of β-Ga_2O_3 are in good agreement with experimental results. Si-and Sn-doped β-Ga_2O_3 tend to form under O-poor conditions, and the formation energy of Si-doped β-Ga_2O_3 is larger than that of Sn-doped β-Ga_2O_3 because of the large bond length variation between Ga–O and Si–O. Si-and Sn-doped β-Ga_2O_3 have wider optical gaps than β-Ga_2O_3, due to the Burstein–Moss effect and the bandgap renormalization effect. Si-doped β-Ga_2O_3 shows better electron conductivity and a higher optical absorption edge than Sn-doped β-Ga_2O_3, so Si is more suitable as a dopant of n-type β-Ga_2O_3, which can be applied in deep-UV photoelectric devices.展开更多
In this work,(-201)β-Ga2O3 films are grown on GaN substrate by metal organic chemical vapor deposition(MOCVD).It is revealed that theβ-Ga2O3 film grown on GaN possesses superior crystal quality,material homogeneity ...In this work,(-201)β-Ga2O3 films are grown on GaN substrate by metal organic chemical vapor deposition(MOCVD).It is revealed that theβ-Ga2O3 film grown on GaN possesses superior crystal quality,material homogeneity and surface morphology than the results of common heteroepitaxialβ-Ga2O3 film based on sapphire substrate.Further,the relevance between the crystal quality of epitaxialβ-Ga2O3 film and theβ-Ga2O3/GaN interface behavior is investigated.Transmission electron microscopy result indicates that the interface atom refactoring phenomenon is beneficial to relieve the mismatch strain and improve the crystal quality of subsequentβ-Ga2O3 film.Moreover,the energy band structure ofβ-Ga2O3/GaN heterostructure grown by MOCVD is investigated by X-ray photoelectron spectroscopy and a large conduction band offset of 0.89 eV is obtained.The results in this work not only convincingly demonstrate the advantages ofβ-Ga2O3 films grown on GaN substrate,but also show the great application potential of MOCVDβ-Ga2O3/GaN heterostructures in microelectronic applications.展开更多
文摘β-Ga2O3作为新型宽禁带半导体材料,近年来受到了人们的广泛关注。β-Ga2O3禁带宽度可达4. 7 e V,相比于第三代半导体SiC和Ga N,具有禁带宽度更大、击穿场强更高、Baliga品质因子更大、吸收截止边更短、生长成本更低的优点,有望成为高压、大功率、低损耗功率器件和深紫外光电子器件的优选材料。此外,β-Ga2O3单晶可以通过熔体法生长,材料制备成本相对较低,有利于大规模应用。重点介绍了β-Ga2O3单晶的生长及工艺优化,然后对晶体加工、性能表征、光电探测及功率器件应用等方面进行了讨论,并展望了β-Ga2O3晶体未来的发展方向。
基金supported by the National Natural Science Foundation of China (No. 20907026)the High Level Talent Research Foundation of Qindao Technological University (No:C-10-210)
文摘Perfluorooctanoic acid （PFOA） is a new-found hazardous persistent organic pollutant, and it is resistant to decomposition by hydroxyl radical （HO.） due to its stable chemical structure and the high electronegativity of fluorine. Photocatalytic reduction of PFOA with β-Ga2O3 in anoxic aqueous solution was investigated for the first time, and the results showed that the photoinduced electron （ecb） coming from the β-Ga2O3 conduction band was the major degradation substance for PFOA, and shorter-chain perfluorinated carboxylic acids （PFCAs, CnF2n＋1COOH, 1 ≤ n ≤ 6） were the dominant products. Furthermore, the concentration of F- was measured by the IC technique and defluorination efficiency was calculated. After 3 hr, the photocatalytic degradation efficiency was 98.8% and defluorination efficiency was 31.6% in the presence of thiosulfate and bubbling N2. The degradation reaction followed first-order kinetics （k = 0.0239 min-1, t1/2 = 0.48 hr）. PFCAs （CnF2n＋xCOOH, 1 ≤ n≤ 7） were detected and measured by LC-MS and LC-MS/MS methods. It was deduced that the probable photocatalytic degradation mechanism involves ec-b attacking the carboxyl of CnF2n＋1COOH, resulting in decarboxylation and the generation of CnFzn＋1. The produced CnF2n＋1 reacted with H2O, forming CnF2n＋1OH, then CnF2n＋1OH underwent HF loss and hydrolysis to form CnF2,＋1COOH.
基金supported by the National Natural Science Foundation of China (Grant No. 10974077)the Natural Science Foundation of Shandong Province, China (Grant No. 2009ZRB01702)the Project of Shandong Province Higher Educational Science and Technology Program (Grant No. J10LA08)
文摘The band structure, density of states, electron density difference and optical properties of intrinsic β-Ga2O3 and N-doped β-Ga2O3 were calculated using first-principles based on density functional theory. After N doping, the band gap decreases, shallow acceptor impurity levels are introduced over the top of the valence band and the absorption band edge is slightly red-shifted compared to that of the intrinsic one. The anisotropic optical properties are investigated by means of the complex dielectric function, which are explained by the selection rule of the band-to-band transitions. All calculation results indicate that N-doping is a very promising method to get P-type β-Ga2O3.
基金supported by the National Natural Science Foundation of China (Grant No. 10974077)the Natural Science Foundation of Shandong Province,China (Grant No. 2009ZRB01702)the Project of Shandong Province Higher Educational Science and Technology Program (Grant No.J10LA08)
文摘The electronic structure and optical properties of N-doped β-Ga2O3 and N-Zn co-doped β-Ga2O3 are investigated by the first-principles calculation. In the N-Zn co-doped β-Ga2O3 system, the lattice parameters of a, b, c, V decrease and the total energy Etot,l increases in comparison with N-doped β-Ga2O3. The calculated ionization energy of N-Zn co-doped β-Ga2O3 is smaller than that of N-doped β-Ga2O3. Two shallower acceptor impurity levels are introduced in N-Zn co-doped β-Ga2O3. Compared with N-doped β-Ga2O3, the major absorption peak is red-shifted and the impurity absorption edge is blue-shifted for N-Zn co-dopedβ-Ga2O3. The results show that the N-Zn co-doped β-Ga2O3 is found to be a better method to push p-type conductivity in β-Ga2O3.
基金the Financial support from the National key Research and Development Program of China(Nso.2018YFB0406502,2016YFB1102201)the National Natural Science Foundation of China(Grant No.51321091)+2 种基金the key Research and Development Program of Shandong Province(No.2018CXGC0410)the Young Scholars Program of Shandong University(No.2015WLJH36)the 111 Project 2.0(No.BP2018013)
文摘As a wide-bandgap semiconductor(WBG), β-Ga_2O_3 is expected to be applied to power electronics and solar blind UV photodetectors. In this review, defects in β-Ga_2O_3 single crystals were summarized, including dislocations, voids, twin, and small defects. Their effects on device performance were discussed. Dislocations and their surrounding regions can act as paths for the leakage current of SBD in single crystals. However, not all voids lead to leakage current. There's no strong evidence yet to show small defects affect the electrical properties. Doping impurity was definitely irrelated to the leakage current. Finally, the formation mechanism of the defects was analyzed. Most small defects were induced by mechanical damages. The screw dislocation originated from a subgrain boundary. The edge dislocation lying on a plane slightly tilted towards the(102) plane, the(101) being the possible slip plane. The voids defects like hollow nanopipes, PNPs, NSGs and line-shaped grooves may be caused by the condensation of excess oxygen vacancies, penetration of tiny bubbles or local meltback. The nucleation of twin lamellae occurred at the initial stage of "shoulder part" during the crystal growth. These results are helpful in controlling the occurrence of crystal defects and improving the device performance.
基金supported by the National Key R&D Program of China(No.2018YFB0406502)the National Natural Science Foundation of China(Nos.61734001,61521004)
文摘Monoclinic gallium oxide(Ga_2O_3) has been grown on(0001) sapphire(Al_2O_3) substrate by plasma-assisted molecular beam epitaxy(PA-MBE). The epitaxial relationship has been confirmed to be [010]( 2ˉ01) β-Ga_2O_3||[ 011ˉ0](0001)Al_2O_3 via in-situ reflection high energy electron diffraction(RHEED) monitoring and ex-situ X-ray diffraction(XRD) measurement. Crystalline quality is improved and surface becomes flatter with increasing growth temperature, with a best full width at half maximum(FWHM) of XRD ω-rocking curve of( 2ˉ01) plane and root mean square(RMS) roughness of 0.68° and 2.04 nm for the sample grown at 730 °C,respectively. Room temperature cathodoluminescence measurement shows an emission at ～417 nm, which is most likely originated from recombination of donor–acceptor pair(DAP).
基金the National Natural Science Foundation of China (Grant Nos. 50472032 and 50672105) the Hundred Talents Program of the Chinese Academy of Sciences
文摘β-Ga2O3: Cr single crystals were grown by floating zone technique. Absorption spectra and fluorescence spectra were measured at room temperature. The values of field splitting parameter Dq and Racah parameter B were obtained by the peak values of absorption spectra. The value 10Dq/B=23.14 manifests that in β-Ga2O3 crystals Cr3+ ions are influenced by low energy crystal field. After high temperature annealing in air, the Cr3+ intrinsic emission was enhanced and the green lumines-cence disappeared. The strong and broad 691 nm emission was obtained at 420 nm excitation due to the electron transition occurred from 4T2 to 4A2. The studies manifest that the β-Ga2O3 crystals have the potential application for tunable laser.
基金Project supported by the Science and Technology Program of Guangdong Province,China(Grant No.2015B010112002)the Science and Technology Project of Guangzhou City,China(Grant No.201607010250)
文摘The electronic structures and optical properties of β-Ga_2O_3 and Si-and Sn-doped β-Ga_2O_3 are studied using the GGA + U method based on density functional theory. The calculated bandgap and Ga 3d-state peak of β-Ga_2O_3 are in good agreement with experimental results. Si-and Sn-doped β-Ga_2O_3 tend to form under O-poor conditions, and the formation energy of Si-doped β-Ga_2O_3 is larger than that of Sn-doped β-Ga_2O_3 because of the large bond length variation between Ga–O and Si–O. Si-and Sn-doped β-Ga_2O_3 have wider optical gaps than β-Ga_2O_3, due to the Burstein–Moss effect and the bandgap renormalization effect. Si-doped β-Ga_2O_3 shows better electron conductivity and a higher optical absorption edge than Sn-doped β-Ga_2O_3, so Si is more suitable as a dopant of n-type β-Ga_2O_3, which can be applied in deep-UV photoelectric devices.
基金supported by the Fundamental Research Funds for the Central Universities(Grant No.JB181108)the National Natural Science Foundation of China(Grant No.61904139)the Science and Technology Program of Guangzhou(Grant No.201904010457)。
文摘In this work,(-201)β-Ga2O3 films are grown on GaN substrate by metal organic chemical vapor deposition(MOCVD).It is revealed that theβ-Ga2O3 film grown on GaN possesses superior crystal quality,material homogeneity and surface morphology than the results of common heteroepitaxialβ-Ga2O3 film based on sapphire substrate.Further,the relevance between the crystal quality of epitaxialβ-Ga2O3 film and theβ-Ga2O3/GaN interface behavior is investigated.Transmission electron microscopy result indicates that the interface atom refactoring phenomenon is beneficial to relieve the mismatch strain and improve the crystal quality of subsequentβ-Ga2O3 film.Moreover,the energy band structure ofβ-Ga2O3/GaN heterostructure grown by MOCVD is investigated by X-ray photoelectron spectroscopy and a large conduction band offset of 0.89 eV is obtained.The results in this work not only convincingly demonstrate the advantages ofβ-Ga2O3 films grown on GaN substrate,but also show the great application potential of MOCVDβ-Ga2O3/GaN heterostructures in microelectronic applications.
