ZnGeP_(2)[ZGP] crystals have attracted tremendous attention for their applications as frequency conversion devices.Nevertheless,the existence of native point defects,including at the surface and in the bulk,lowers the...ZnGeP_(2)[ZGP] crystals have attracted tremendous attention for their applications as frequency conversion devices.Nevertheless,the existence of native point defects,including at the surface and in the bulk,lowers their laser-induced damage threshold by increasing their absorption and forming starting points of the damage,limiting their applications.Here,native point defects in a ZGP crystal are fully studied by the combination of high angle annular dark-field scanning transmission electron microscopy[HAADF-STEM] and optical measurements.The atomic structures of the native point defects of the Zn vacancy,P vacancy,and Ge-Zn antisite were directly obtained through an HAADF-STEM,and proved by photoluminescence[PL] spectra at 77 K.The carrier dynamics of these defects are further studied by ultrafast pump-probe spectroscopy,and the decay lifetimes of 180.49,346.73,and 322.82 ps are attributed to the donor V_(p)^(+)→valence band maximum[VBM] recombination,donor Ge^(+)_(Zn)→VBM recombination,and donor–acceptor pair recombination of V_(p)^(+)→V^(-)_(Zn),respectively,which further confirms the assignment of the electron transitions.The diagrams for the energy bands and excited electron dynamics are established based on these ultrahigh spatial and temporal results.Our work is helpful for understanding the interaction mechanism between a ZGP crystal and ultrafast laser,doing good to the ZGP crystal growth and device fabrication.展开更多
A high-quality ZnGeP_(2)(ZGP)single crystal with large size ofΦ30 mm×80 mm was grown by a modified vertical Bridgman method.ZGP wafers were annealed with ZGP polycrystalline powder for 300 h at 550,600 and 650℃...A high-quality ZnGeP_(2)(ZGP)single crystal with large size ofΦ30 mm×80 mm was grown by a modified vertical Bridgman method.ZGP wafers were annealed with ZGP polycrystalline powder for 300 h at 550,600 and 650℃,respectively.The as-grown and annealed crystals were characterized by X-ray diffraction(XRD)analysis,Fourier transform infrared spectroscopy(FTIR),IR microscope and energy-dispersive spectroscopy(EDS).Results show that the quality of all wafers is improved evidently after annealing and the optimum annealing temperature obtained is 600℃.The IR transmittance of the wafer measured by FTIR is up to 56.78%at wavelength of 2.0μm nearby and exceeds 59.00%in the wavelength range of 3.0-8.0μm.The deviations from stoichiometry decrease,and the homogeneity of the crystal is also improved after annealing.In this paper,scanning infrared map was proposed as a new nondestructive method to evaluate optical quality and homogeneity of crystal through comparing the IR transmittance with the three-dimensional IR spectral contour map.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51872198,52172151,52172002,92163207,51972229,and 51890865)the Natural Science Foundation of Tianjin(No.18JCYBJC42500)+1 种基金the National Defense Science and Technology 173 Program(No.2021-JCJQJJ-0639)the Natural Science Foundation of Heilongjiang Province(No.YQ2020B002)。
文摘ZnGeP_(2)[ZGP] crystals have attracted tremendous attention for their applications as frequency conversion devices.Nevertheless,the existence of native point defects,including at the surface and in the bulk,lowers their laser-induced damage threshold by increasing their absorption and forming starting points of the damage,limiting their applications.Here,native point defects in a ZGP crystal are fully studied by the combination of high angle annular dark-field scanning transmission electron microscopy[HAADF-STEM] and optical measurements.The atomic structures of the native point defects of the Zn vacancy,P vacancy,and Ge-Zn antisite were directly obtained through an HAADF-STEM,and proved by photoluminescence[PL] spectra at 77 K.The carrier dynamics of these defects are further studied by ultrafast pump-probe spectroscopy,and the decay lifetimes of 180.49,346.73,and 322.82 ps are attributed to the donor V_(p)^(+)→valence band maximum[VBM] recombination,donor Ge^(+)_(Zn)→VBM recombination,and donor–acceptor pair recombination of V_(p)^(+)→V^(-)_(Zn),respectively,which further confirms the assignment of the electron transitions.The diagrams for the energy bands and excited electron dynamics are established based on these ultrahigh spatial and temporal results.Our work is helpful for understanding the interaction mechanism between a ZGP crystal and ultrafast laser,doing good to the ZGP crystal growth and device fabrication.
基金financially supported by the National Natural Science Foundation Key Programs of China(No.50732005)the National High Technology Research and Development Program of China(No.2007AA03Z443)。
文摘A high-quality ZnGeP_(2)(ZGP)single crystal with large size ofΦ30 mm×80 mm was grown by a modified vertical Bridgman method.ZGP wafers were annealed with ZGP polycrystalline powder for 300 h at 550,600 and 650℃,respectively.The as-grown and annealed crystals were characterized by X-ray diffraction(XRD)analysis,Fourier transform infrared spectroscopy(FTIR),IR microscope and energy-dispersive spectroscopy(EDS).Results show that the quality of all wafers is improved evidently after annealing and the optimum annealing temperature obtained is 600℃.The IR transmittance of the wafer measured by FTIR is up to 56.78%at wavelength of 2.0μm nearby and exceeds 59.00%in the wavelength range of 3.0-8.0μm.The deviations from stoichiometry decrease,and the homogeneity of the crystal is also improved after annealing.In this paper,scanning infrared map was proposed as a new nondestructive method to evaluate optical quality and homogeneity of crystal through comparing the IR transmittance with the three-dimensional IR spectral contour map.
