【作者】 曹昆；

【导师】 贾刚； 陈占国；

【作者基本信息】 吉林大学 ， 微电子学与固体电子学， 2008， 博士

【摘要】 本论文介绍了立方氮化硼线性电光效应和紫外光电效应的研究过程和研究结果。作者首先对两个方面的相关理论进行了阐述,之后结合材料自身的特点给出了具体的实验方案,并对实验的主要过程进行了叙述,最后结合理论对实验结果进行了分析。本论文克服了目前缺少大尺寸cBN单晶给研究者带来的困难,根据微小尺寸cBN晶体的实际形状设计出了一个考虑了cBN单晶微小尺寸和片状八面体外形的电极装置,在经典的横向电光调制器基础上对调制器的结构做了一些调整,在实验中用650nm连续波半导体激光器在cBN单晶上实现了横向电光调制,通过得到的横向电光调制半波电压计算出了cBN单晶的线性电光张量和二阶非线性极化率张量。由于实验中在个别样品上发现有静态相位延迟,作者对静态相位延迟的产生进行了分析,并通过理论推导和计算,提出了一种补偿静态相位延迟的简便方法。在实现了横向电光调制后,作者研究了如何用微小尺寸片状八面体cBN单晶作为探头应用到集成电路的外部电光检测技术中。通过理论计算和对样品几何形状的分析,得出了片状八面体cBN单晶探头在待测电场中应该如何确定方向,之后用片状八面体cBN单晶作为探头对陶瓷微带线中的信号进行了外部电光检测,检测结果与陶瓷微带线中的被测信号相吻合。基于研制立方氮化硼紫外光电探测器的需要,本文对立方氮化硼的紫外光电效应进行了研究。作者首先从理论上研究了立方氮化硼产生光电效应的物理机制,之后用cBN单晶制作了MSM结构的样品,并分别用氘灯和248nm准分子激光器作为光源,研究了MSM结构cBN样品的光电响应。实验发现当样品贴近氘灯的MgF窗口时有光电响应;样品在光功率密度较低的248nm的准分子激光照射下没有光响应,但是如果不断提高照射到样品有效接收面积上的准分子激光的光强,能够观察到样品的光响应。作者认为用氘灯做光源时样品以单光子吸收为主,用248nm波长的准分子激光做光源时样品以倍频吸收为主。实验还测量了样品在准分子激光照射下的击穿电压和从开始照射到发生击穿现象经历的时间。击穿过程中样品没有损坏,击穿现象可以重复。研究结果为进一步研制“日盲型”cBN紫外光电探测器奠定了基础。更多还原

【Abstract】 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.更多还原