| Cubic boron nitride (cBN) is a kind of artificial crystal synthesized at high pressure and high temperature. Inartificial cBN has not been found in nature so far. cBN crystal is similar to diamond in terms of mechanical hardness, melt point and thermal conductivity. So it is a very good material for abrasives and cutting tools. cBN is also a kind of wide bandgap semiconductor material, the bandgap of cBN is indirect and about 6.3 eV. Both p-type and n-type cBN crystals can be obtained when suitable impurities are doped. cBN has zinc blende structure with 4 3m symmetry, thus, it possesses second-order nonlinear optical properties, and can be used as the nonlinear optical material. Moreover, cBN is transparent within the whole visible and most ranges of infrared and ultraviolet spectra. So cBN has great potential in high-frequency, high-temperature, and high-power electronic devices, especially in ultraviolet (UV) optoelectronic devices.Because it is difficult to synthesize large-size and high quality cBN crystals at present, so there are deficient researches and applications on nonlinear optical properties and semiconductor properties of cBN by now. A transverse electro-optical (EO) modulator based on a tiny octahedral wafer of cBN crystal was demonstrated, cBN crystal was prepared by hexagonal boron nitride at high pressure and high temperature using nitride as catalyst. The half-wave voltage based on experiments of transverse electro-optical modulation was obtained. The second-order nonlinear optical susceptibilityχi(j k2 )(ω,0)=1.919×10?12mV of cBN crystal was calculated by means of the half-wave voltage. In addition, the meatel-semiconductor-metal (MSM) sample based on cBN crystal with Schottky contact was manufactured, the ultraviolet photoelectric effect of cBN was investigated. The results laid the foundation for further development of solar-blind ultraviolet detector based on cBN crystal.Because the synthesis of cBN crystal is extremely difficult, the synthetic single crystals we can obtain are very small and have irregular forms, whose maximal size is about 0.5 mm only. Moreover, cBN is a kind of super-hard material, and can not be cut into rectangular parallelepiped easily. So, traditional EO modulation techniques are unsuitable for cBN crystals. We choose an octahedral cBN crystal wafer as sample, scheme out a novel electrode fabrication taking account of the small size and octahedral shape of cBN crystals, and introduce a developed method different from the conventional transverse EO modulator. The expression of the intensity of output beam when the input beam and the output beam do not propagate vertically to the end plane of EO crystal is thought over, and we investigate the best working condition in which the transverse EO modulator meet the best linearity and sensitivity. Then we obtain the half-wave voltage based on experiments of transverse electro-optical modulation. Finally, we figure out the second-order nonlinear optical susceptibility of cBN crystal, it isχi(j 2k )(ω,0)=1.919×10?12mV. This simple method eliminates the need for bulky crystal, moreover it is unnecessary to apply high modulation voltage and measure the absolute intensity of probing beam. So, it is very convenient and effective. We also investigate the cause of static phase retardation, and introduce a simple method compensating the static phase retardation through theory and theoretical calculations.The application of EO measuring based on octahedral cBN crystal wafer was investigated after the second-order nonlinear optical susceptibility was determined. According to the analysis of the geometry and theoretical calculations, octahedral cBN crystal wafer, as an EO probe, should be adjusted so that its [1 10] or [1 12] direction is parallel to the direction of electric field Thus, the syetem of EO measuring meet the best sensitivity. We use an octahedral cBN crystal wafer as an EO probe for measuring the electric signal of the ceramic microstrip, the measured signal agree with the real signal propagating on the ceramic microstrip.The physical mechanism of ultraviolet photoelectric effect of cBN is researched too, we believe that the ultraviolet photoelectric effect of cBN is caused by both the single-photon response and the two-photon response. Then we manufacture a meatel-semiconductor-metal (MSM) sample based on cBN crystal with Schottky contact, and test the photoelectric response under the irradiation of deuterium lamp and excimer laser at the wavelength of 248nm. We obtain the I-V curve when the cBN MSM sample is close to the MgF window. cBN MSM sample has no photoelectric response under the irradiation of excimer laser at the wavelength of 248nm when the optical power density is low. If we enhance the optical power density of excimer laser, the photoelectric response of the cBN MSM sample is observed. We believe that the excimer laser reach to cBN along with [1 11] direction lead to second harmonic generation when the optical power density is enough.In order to research the cBN MSM sample working in condition of critical state of avalanche breakdown, high bias was applied to cBN MSM sample subsequently. If we make cBN MSM sample under the irradiation of excimer laser at the wavelength of 248nm and enhance the optical power density of excimer laser at the same time, cBN MSM sample become avalanche breakdown when the voltage of bias is 817V. (the breakdown voltage of cBN MSM sample is 1170V when there is no irradiation of light source) The phenomenon of breakdown can repeat.We measured the current before and after breakdown happened separately, and measured the time from turing on excimer laser to happening breakdown phenomenon. These results laid the foundation for further development of solar-blind ultraviolet detector based on cBN crystal.
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