High quality 0.02 mol%,0.05 mol%,and 0.08 mol%Fe:β-Ga2O3 single crystals were grown by the floating zone method.The crystal structure,optical,electrical,and thermal properties were measured and discussed.Fe:β-Ga2O3 ...High quality 0.02 mol%,0.05 mol%,and 0.08 mol%Fe:β-Ga2O3 single crystals were grown by the floating zone method.The crystal structure,optical,electrical,and thermal properties were measured and discussed.Fe:β-Ga2O3 single crystals showed transmittance of higher than 80%in the near infrared region.With the increase of the Fe doping concentration,the optical bandgaps reduced and room temperature resistivity increased.The resistivity of 0.08 mol%Fe:β-Ga2O3 crystal reached to 3.63×1011Ω·cm.The high resistivity Fe:β-Ga2O3 single crystals could be applied as the substrate for the high-power field effect transistors(FETs).展开更多
The rapid development of bulk β-Ga_2O_3 crystals has attracted much attention to their use as ultra-wide bandgap materials for next-generation power devices owing to its large bandgap(~ 4.9 eV) and large breakdown e...The rapid development of bulk β-Ga_2O_3 crystals has attracted much attention to their use as ultra-wide bandgap materials for next-generation power devices owing to its large bandgap(~ 4.9 eV) and large breakdown electric field of about8 MV/cm. Low cost and high quality of large β-Ga_2O_3 single-crystal substrates can be attained by melting growth techniques widely used in the industry. In this paper, we first present an overview of the properties of β-Ga_2O_3 crystals in bulk form. We then describe the various methods for producing bulk β-Ga_2O_3 crystals and their applications. Finally, we will present a future perspective of the research in the area in the area of single crystal growth.展开更多
β-Ga2O3∶Cr single crystals have potential applications for tunable laser. In β-Ga2O3 crystal structure Cr3+ ions are in octahedron other than tetrahedron. So the Cr3+ ions are influenced by low field of β-Ga2O3 th...β-Ga2O3∶Cr single crystals have potential applications for tunable laser. In β-Ga2O3 crystal structure Cr3+ ions are in octahedron other than tetrahedron. So the Cr3+ ions are influenced by low field of β-Ga2O3 that results the 4T2 to 4A2 transition and show broad emission around 690 nm. β-Ga2O3 single crystals doped with different Cr3+ concentrations were grown by floating zone technique. Their absorption spectra and fluorescence spectra were measured at room temperature. The values of field splitting parameter Dq and Racah parameter B were calculated based on the absorption spectra.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
Ta5+doped β-Ga2O3 single crystals were grown by using the optical floating zone method, and then annealed in the air and nitrogen gas at 1400℃ for 20 hours.The transmittance spectra, photoluminescence(PL), x-ray irr...Ta5+doped β-Ga2O3 single crystals were grown by using the optical floating zone method, and then annealed in the air and nitrogen gas at 1400℃ for 20 hours.The transmittance spectra, photoluminescence(PL), x-ray irradiation spectra, and PL decay profiles of the samples were measured at room temperature.The relevant results show that the optical transmittance of the samples annealed in the air or nitrogen gas was improved.By drawing the(ahv)2–hv graph,it can be seen that the band gap decreased after being annealed in the air, but increased in nitrogen gas.The PL spectra and x-ray irradiation spectra show that the luminescent intensity of the sample annealed in the air increased substantially,while decreased for the sample annealed in nitrogen.The PL decay time of the Ta:β-Ga2O3 annealed in the air increased significantly compared with that of the Ta:β-Ga2O3 sample without annealing, but the tendency after annealing in nitrogen gas was opposite.展开更多
The crystallization behavior and kinetics of CaO-MgO-Al2O3 SiO2(CMAS) glass with the Fe2O3 content ranging from zero to 5%were investigated by differential scanning calorimetry(DSC).The structure and phase analyse...The crystallization behavior and kinetics of CaO-MgO-Al2O3 SiO2(CMAS) glass with the Fe2O3 content ranging from zero to 5%were investigated by differential scanning calorimetry(DSC).The structure and phase analyses were made by Fourier transform infrared spectroscopy(FT-IR) and X-ray diffraction(XRD).The experiment results show that the endothermic peak temperature about 760℃ is associated with transition and the exothermic peak temperature about 1000℃ is associated with crystallization.The crystallization peak temperature decreases with increasing the Fe203 content.The crystallization mechanism is changed from two-dimensional crystallization to one-dimensional growth,and the intensity of diopside peaks becomes stronger gradually.There is a saltation for the crystallization temperature with the addition of 0.5%Fe2O3 due to the decomposition of Fe2O3.Si-O-Si,O-Si-O and T-O-T(T=Si,Fe,Al) linkages are observed in Fe2O3-CaO-MgO-Al2O3-SiO2 glass.展开更多
Four crystals with the general formula of A3BGa3Si2O14 (A = Ca^2+, Sr^2+; B=Nb^5+ , Ta^5+) grown by using the Czoehralsky technique were reported. They are all uniaxial and belong to 32 point group. Their transm...Four crystals with the general formula of A3BGa3Si2O14 (A = Ca^2+, Sr^2+; B=Nb^5+ , Ta^5+) grown by using the Czoehralsky technique were reported. They are all uniaxial and belong to 32 point group. Their transmission, rotatory angle and specific rotation dispersion were investigated by speetrophotometer and compared with LGS. The transmission spectra show that they are transparent in the visible wavelength region beyond 294 nm and infrared region, and their transmission are all larger than that of LGS.The transmission spectra between parallel polasizers show that they have large optical activities which are larger than that of LGS. Of the four crystals, Sr3NbGa3Si2O14 has the largest optical activity : 240.75 (°)·mm^-1 at 0.30 μm wavelength, 34.73 (°) ·mm^-1 at 0. 633 μm wavelength. The Bohzmann's coefficients of these crystals were calculated, which were in good agreement with earlier measurement in other reference.展开更多
The title compound, Cs 2[Mg(CO 3) 2(H 2O) 4], was synthesized by the dropwise addition of an aqueous solution of Mg(NO 3) 2 to a stirred aqueous Cs 2CO 3/CsHCO 3 solution. A colorless needle shaped crystal was formed ...The title compound, Cs 2[Mg(CO 3) 2(H 2O) 4], was synthesized by the dropwise addition of an aqueous solution of Mg(NO 3) 2 to a stirred aqueous Cs 2CO 3/CsHCO 3 solution. A colorless needle shaped crystal was formed by slow evaporation. The crystal structure was established on the basis of the single crystal X ray diffraction data. Cs 2[Mg(CO 3) 2(H 2O) 4] crystallized in the orthorhombic space group Pbca (No. 61) with a =0.658 4(1) nm, b =1.257 9(1) nm, c =1.301 3(1) nm, \{ V =1.077 8 nm 3, Z =4, D x=2.971 g·cm -3 , μ =69.20 cm -1 , F (000)=888, T =298 K, final R =0.029 and R w=0.024 for 1 037 observed reflections. The crystal consists of Cs + cations and the complex trans [Mg(CO 3) 2(H 2O) 4] 2- anions with each Mg atom coordinated by the six oxygens of two carbonate groups and four water molecules [ d (Mg_O)=0.203 6(4), 0.207 4(4), 0.213 4(4) nm]. The complex trans [Mg(CO 3) 2(H 2O) 4] 2- anions are arranged in a strongly compressed bcc pattern. A 3D network was formed through the intermolecular hydrogen bonds. The Cs + cations are located in cavities, each being surrounded by nine oxygens of five complex anions with d (Cs_O)=0.306 1-0.348 8 nm. The CO 2- 3 group reveals a lowering of D 3h symmetry due to site and coordination effects, but not any observable deviation from co planarity [ d (C_O)=0.127 2(6), 0.127 5(7) , 0.130 5(6) nm and O_C_O=119.6(5)°, 120.1(5)°, 120.4(5)°].展开更多
基金the Scientific and Innovative Action Plan of Shanghai,China(Grant No.18511110502)Equipment Pre-research Fund Key Project,China(Grant No.6140922010601).
文摘High quality 0.02 mol%,0.05 mol%,and 0.08 mol%Fe:β-Ga2O3 single crystals were grown by the floating zone method.The crystal structure,optical,electrical,and thermal properties were measured and discussed.Fe:β-Ga2O3 single crystals showed transmittance of higher than 80%in the near infrared region.With the increase of the Fe doping concentration,the optical bandgaps reduced and room temperature resistivity increased.The resistivity of 0.08 mol%Fe:β-Ga2O3 crystal reached to 3.63×1011Ω·cm.The high resistivity Fe:β-Ga2O3 single crystals could be applied as the substrate for the high-power field effect transistors(FETs).
基金funded by the following grants:Chinese Academy of Sciences president’s International Fellowship Initiative(Grant No.2018PE0033)National Natural Science Foundation of China(Grant No.51802327)+1 种基金Science and Technology Commission of Shanghai Municipality(No.18511110500)Pre-research Fund Key Project(No.6140922010601)
文摘The rapid development of bulk β-Ga_2O_3 crystals has attracted much attention to their use as ultra-wide bandgap materials for next-generation power devices owing to its large bandgap(~ 4.9 eV) and large breakdown electric field of about8 MV/cm. Low cost and high quality of large β-Ga_2O_3 single-crystal substrates can be attained by melting growth techniques widely used in the industry. In this paper, we first present an overview of the properties of β-Ga_2O_3 crystals in bulk form. We then describe the various methods for producing bulk β-Ga_2O_3 crystals and their applications. Finally, we will present a future perspective of the research in the area in the area of single crystal growth.
基金Project supported by the National Natural Science Foundation of China (50472032) and Hundred Talents Program of Chinese Academy of Sciences
文摘β-Ga2O3∶Cr single crystals have potential applications for tunable laser. In β-Ga2O3 crystal structure Cr3+ ions are in octahedron other than tetrahedron. So the Cr3+ ions are influenced by low field of β-Ga2O3 that results the 4T2 to 4A2 transition and show broad emission around 690 nm. β-Ga2O3 single crystals doped with different Cr3+ concentrations were grown by floating zone technique. Their absorption spectra and fluorescence spectra were measured at room temperature. The values of field splitting parameter Dq and Racah parameter B were calculated based on the absorption spectra.
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Project supported by the National Natural Science Foundation of China(Grant No.51802327)the Science and Technology Commission of Shanghai Municipality,China(Grant No.18511110500)
文摘Ta5+doped β-Ga2O3 single crystals were grown by using the optical floating zone method, and then annealed in the air and nitrogen gas at 1400℃ for 20 hours.The transmittance spectra, photoluminescence(PL), x-ray irradiation spectra, and PL decay profiles of the samples were measured at room temperature.The relevant results show that the optical transmittance of the samples annealed in the air or nitrogen gas was improved.By drawing the(ahv)2–hv graph,it can be seen that the band gap decreased after being annealed in the air, but increased in nitrogen gas.The PL spectra and x-ray irradiation spectra show that the luminescent intensity of the sample annealed in the air increased substantially,while decreased for the sample annealed in nitrogen.The PL decay time of the Ta:β-Ga2O3 annealed in the air increased significantly compared with that of the Ta:β-Ga2O3 sample without annealing, but the tendency after annealing in nitrogen gas was opposite.
基金Projects(51264023,51364020,U1202271)supported by the National Natural Science Foundation of ChinaProject(IRT1250)supported by the Program for Innovative Research Team in University of Ministry of Education of ChinaProject(2014HA003)supported by the Science and Technology Leading Talent of Yunnan Province,China
文摘The crystallization behavior and kinetics of CaO-MgO-Al2O3 SiO2(CMAS) glass with the Fe2O3 content ranging from zero to 5%were investigated by differential scanning calorimetry(DSC).The structure and phase analyses were made by Fourier transform infrared spectroscopy(FT-IR) and X-ray diffraction(XRD).The experiment results show that the endothermic peak temperature about 760℃ is associated with transition and the exothermic peak temperature about 1000℃ is associated with crystallization.The crystallization peak temperature decreases with increasing the Fe203 content.The crystallization mechanism is changed from two-dimensional crystallization to one-dimensional growth,and the intensity of diopside peaks becomes stronger gradually.There is a saltation for the crystallization temperature with the addition of 0.5%Fe2O3 due to the decomposition of Fe2O3.Si-O-Si,O-Si-O and T-O-T(T=Si,Fe,Al) linkages are observed in Fe2O3-CaO-MgO-Al2O3-SiO2 glass.
文摘Four crystals with the general formula of A3BGa3Si2O14 (A = Ca^2+, Sr^2+; B=Nb^5+ , Ta^5+) grown by using the Czoehralsky technique were reported. They are all uniaxial and belong to 32 point group. Their transmission, rotatory angle and specific rotation dispersion were investigated by speetrophotometer and compared with LGS. The transmission spectra show that they are transparent in the visible wavelength region beyond 294 nm and infrared region, and their transmission are all larger than that of LGS.The transmission spectra between parallel polasizers show that they have large optical activities which are larger than that of LGS. Of the four crystals, Sr3NbGa3Si2O14 has the largest optical activity : 240.75 (°)·mm^-1 at 0.30 μm wavelength, 34.73 (°) ·mm^-1 at 0. 633 μm wavelength. The Bohzmann's coefficients of these crystals were calculated, which were in good agreement with earlier measurement in other reference.
文摘The title compound, Cs 2[Mg(CO 3) 2(H 2O) 4], was synthesized by the dropwise addition of an aqueous solution of Mg(NO 3) 2 to a stirred aqueous Cs 2CO 3/CsHCO 3 solution. A colorless needle shaped crystal was formed by slow evaporation. The crystal structure was established on the basis of the single crystal X ray diffraction data. Cs 2[Mg(CO 3) 2(H 2O) 4] crystallized in the orthorhombic space group Pbca (No. 61) with a =0.658 4(1) nm, b =1.257 9(1) nm, c =1.301 3(1) nm, \{ V =1.077 8 nm 3, Z =4, D x=2.971 g·cm -3 , μ =69.20 cm -1 , F (000)=888, T =298 K, final R =0.029 and R w=0.024 for 1 037 observed reflections. The crystal consists of Cs + cations and the complex trans [Mg(CO 3) 2(H 2O) 4] 2- anions with each Mg atom coordinated by the six oxygens of two carbonate groups and four water molecules [ d (Mg_O)=0.203 6(4), 0.207 4(4), 0.213 4(4) nm]. The complex trans [Mg(CO 3) 2(H 2O) 4] 2- anions are arranged in a strongly compressed bcc pattern. A 3D network was formed through the intermolecular hydrogen bonds. The Cs + cations are located in cavities, each being surrounded by nine oxygens of five complex anions with d (Cs_O)=0.306 1-0.348 8 nm. The CO 2- 3 group reveals a lowering of D 3h symmetry due to site and coordination effects, but not any observable deviation from co planarity [ d (C_O)=0.127 2(6), 0.127 5(7) , 0.130 5(6) nm and O_C_O=119.6(5)°, 120.1(5)°, 120.4(5)°].