【作者】 刘海波；

【导师】 贾刚；

【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】 本文从理论和实验两个方面对于立方氮化硼(Cubic Boron Nitride,cBN)的半导体特性进行了研究。利用第一性原理的GGA方法(梯度校正局域密度泛函)计算了能带结构,得到了电子态密度和＜100＞、＜110＞和＜111＞方向的电荷密度,对基于密度泛函法的能量计算负偏差这一经验事实,通过紫外吸收光谱的实验结果予以修正,给出了6.26eV(误差0.01eV)的实验结果。所得到的非直接带隙的能带结构为理论上研究电致发光奠定了基础。其次,利用基本的I-V关系实验研究了cBN的导电行为,引入1.5%的陷阱浓度后,在弱电场的条件下,发现I-V关系与空间电荷限制电流理论非常吻合。另外,结合束缚电流建立时间的测试和缺陷偶极子的取向极化电介质特性,提出了电压击穿的二个阶段模型。同时,研究了cBN导电性的温度依赖关系,发现了在典型的半导体温度特性过程后导电特性的高达几个数量级变化的电流峰。进行了Hall特性和热激电流谱的研究,发现在导带下面0.57eV处存在杂质能级,分析认为是材料在合成时的缺陷所致。本文重要的实验发现是当电场强度达到4.8×10~6V/cm时,电流出现不稳定现象,进一步增加场强,将发生电击穿。击穿后,cBN具有极大的电导率,当电场强度增大到10~2V/cm时,其电流密度高达10A/cm~2,同时伴有强烈的辐射发光。发光过程中,材料温度急剧增加,回路电流有周期为ns级的电流振荡现象,测量结果表明辐射发光为脉冲光。针对这一实验现象,利用带隙发光理论和电介质击穿理论,提出了基本的理论模型,较好地解释了发光机理。本文的理论和实验研究结果是开展cBN半导体器件、紫外激光器及探测器研究的基础工作,具有十分重要的意义。更多还原

【Abstract】 The cube boron nitride crystal（c-BN）is another new ultra hard material which the humanity gets by the high temperature pressure technique synthesis after the artificial diamond.It is the typicalⅢ-Ⅴraces nitride,has the sphalerite structure,and the macroscopic symmetry belongs to the group^（?）3m. It has the outstanding physical chemistry performance,besides the chemical stability surpasses the diamond and the degree of hardness is inferior to diamond,it has wide energy gap（about 6.4eV）,the low coefficient of dielectric loss,the heat conductivity as high as 13W/cm.K theoretically （experiment to obtain maximum heat conductivity 7.4W/cm.K）,and the possibility to be doped p and n forms semiconducting material and so on causes it is applied to many domains,especially photoelectric apparatus,high temperature component,microwave device etc.Therefore,the research regarding the c-BN semiconductor characteristic has the very vital significance.But as a result of the c-BN material size to measuring technique’s limit,this aspect’s related reports are not many.This paper carries on a research to the semi-conductor characteristic of square Boron Nitride in the theories and experimentation.First,calculate the band-gap structure using the GGA method（gradient correction Local Density Functional Theory）of the first-principle methods;get the density of electronic state and the density of electron number with the direction of（100）,（110）and （111）.For the experienced result of the partial negative energy calculated based on the density functional method,we correct it with experimental result of ultraviolet absorption spectrum,we get the result of 6.3eV with the error of 0.1eV.The non-direct band gap energy band structure theory laid the foundation for the research of electroluminescence.Secondly,study on the c-BN conductivity by using of basic j-E relation experimental,and with its characteristic electrolyte,raise the two-phase model of the breakdown voltage. Meanwhile,the several orders of magnitude current peaks of the conductivity properties have been found after the process of a typical semiconductor temperature characteristic by research about the c-BN conductivity of the temperature dependence.Through the research of the Hall characteristics and the heat shock current spectrum,found impurity level in the 0.56eV under the conduction band,analysts believe that it is induced by the defect in the material synthesis.In this paper,we find that when the strength of electric field was up to 4.8×10⁶V/cm,the current become instable,and if the strength of electric field was increased continually,there would be a electric breakdown.After the electric breakdown,the conductivity of c-BN will be too great,and when the strength of electric field increased to 10²V/cm,the current density would be up to 10A/cm²,accompanied by strong radio luminescence.At the same time, the temperature of the materials was increased rapidly;and the loop current oscillates at the periodicity of some nanosecond,the measurement results show that was the pulsed light.According to this phenomenon,using of the theory of band gap luminescence and dielectric breakdown,we give the basic theoretical model to explain the luminescence mechanism.In this paper,the theoretical and experimental result is of great significance,for it is the basic work for deeply research of c-BN semiconductor devices,ultraviolet laser and detector.更多还原