共查询到19条相似文献,搜索用时 62 毫秒
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给出了n型和p型4H-SiC的二级喇曼谱的实验结果.指认了所观察到的一些光谱结构对应的特定声子支及其在布里渊区中相应的对称点.发现在4H-SiC的二级喇曼谱中存在能量差约为10cm-1 的双谱线结构,这一结构与六方相GaN,ZnO和AlN的双谱线结构具有相同的能量差.二级喇曼谱的截止频率对于不同掺杂情况的4H-SiC具有相同的值.它并不等于n型掺杂4H-SiC的A1(LO)声子的倍频,而是等于未掺杂样品的A1(LO)声子的倍频.掺杂类型和杂质浓度对4H-SiC的二级喇曼谱几乎没有影响. 相似文献
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ZrO2·SiO2·P2O5半导陶瓷是由ZrO2、SiO2和H3PO4用高温固相反应制成.它的傅里叶红外吸收谱是由ZrO2和SiO2的标准谱叠加而成.根据标准峰的位置分别计算出两种氧化物的四个基本声子能量.这些声子按照不同组合方式形成ZrO2·SiO2·P2O5半导陶瓷的全部傅里叶红外吸收峰.半导陶瓷的喇曼背向散射峰也是由这些基本声子组合而成.对比四角和单斜ZrO2的喇曼特征谱线看出,在未掺杂和用Y2O3或Nb2O5掺杂的半导陶瓷样品中,ZrO2的晶粒微结构分别属于单斜和四角对称晶系. 相似文献
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用电子能量损失谱(EELS)研究了金刚石膜、类金刚石膜和高取向石墨的特征能量损失峰.金刚石膜的特征峰主要是5.4eV和15eV的带间跃迁,23eV和34eV的表面等离子激元和体等离子激元.类金刚石膜的特征峰主要是 4.5eV的π电子的体等离子激元,13eV的带间跃迁,22.4eV的(π+ σ)电子的体等离子激元.石墨的特征峰主要是6eV的π电子的等离子激元,13eV带间跃迁和C轴方向等离子激元,20eV的C轴方向的等离子激元和25.6eV的基面等离子激元.比较了α-C和α-C:H能量损失谱和喇曼光谱,利用hω_(p(π+σ))和hω_(p(x))峰位计算了类金刚石膜中sp~3键和sp~2键的比例.研究了不同CH_4浓度生长的金刚石膜的能量损失谱,利用hω_(p(π+σ))和hω_(p(x))峰位计算金刚石膜中类金刚石第二相内的sp~2键和sp~3键的比例,利用第二相的体等离子激元损失峰hω_(p(π+σ))与金刚石的体等离子激元损失峰hω_(p(σ))的强度比来估价第二相的多少. 相似文献
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为了发展具有实用价值的受激喇曼全光偏振控制方法,根据光纤中受激喇曼散射矢量理论和光纤随机双折射效应设计了基于双向二级喇曼抽运的全光偏振控制方案,构建了偏振吸引理论模型,采用严格数值迭代算法对该偏振控制方案进行了仿真分析,并完成了偏振控制方案最佳工作性能的优化设计。结果表明,当信号光波长为1550nm、功率为0.1mW、一级抽运光和二级抽运光的功率分别为1W和4W、其偏振态都为(0,1,0)、光纤长度为3km时,信号光偏振度可达0.85以上,且信号光强度波动低于35%。该方案有效降低了作用光波功率、减弱了信号光输出强度噪声,并提高了信号光输出偏振度。 相似文献
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对在GaAs、Al2O3和Si等衬底上MOCVD技术生长的GaN薄膜进行了背散射几何配置下的喇曼散射测试分析和比较,观察到α相GaNl模,Al模El模和E2模,结合射线衍射谱,分析了因不同生长工艺导致GaN/GaAs样品的不同结构相的喇曼谱的差异,发现GaN喇曼谱与GaN外延层的结构相,完整性及工艺条件有关,可利用其作为检测GaN外延层结构特性的一种有用手段。 相似文献
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Kazuhiro Ito Toshitake Onishi Hidehisa Takeda Kazuyuki Kohama Susumu Tsukimoto Mitsuru Konno Yuya Suzuki Masanori Murakami 《Journal of Electronic Materials》2008,37(11):1674-1680
The fabrication procedure for silicon carbide power metal oxide semiconductor field-effect transistors can be improved through
simultaneous formation (i.e., using the same contact materials and a one-step annealing process) of ohmic contacts on both
the n-source and p-well regions. We have succeeded in the simultaneous formation of Ni/Al ohmic contacts to n- and p-type SiC after annealing at 1000°C for 5 min in an ultrahigh vacuum. Ohmic contacts to n-type SiC were found when the Al-layer thickness was less than about 6 nm, while ohmic contacts to p-type SiC were observed for an Al-layer thickness greater than about 5 nm. Only the contacts with an Al-layer thickness in
the range of 5 nm to 6 nm exhibited ohmic behavior to both n- and p-type SiC, with a specific contact resistance of 1.8 × 10−4 Ω cm2 and 1.2 × 10−2 Ω cm2 for n- and p-type SiC, respectively. An about 100-nm-thick contact layer was uniformly formed on the SiC substrate, and polycrystalline
δ-Ni2Si(Al) grains were formed at the contact/SiC interface. In the samples that exhibited ohmic behavior to both n- and p-type SiC, the distribution of the Al/Ni ratios in the δ-Ni2Si(Al) grains was larger than that observed for any of the samples that showed ohmic behavior to either n- or p-type SiC. Furthermore, the grain size of the δ-Ni2Si(Al) grains in the samples showing ohmic behavior to both n- and p-type SiC was smaller than the grains in any of the samples that showed ohmic behavior to either n- or p-type SiC. Thus, the large distribution in the Al/Ni ratios and a fine microstructure were found to be characteristic of the
ohmic contacts to both n- and p-type SiC. Grains with a low Al concentration correspond to ohmic contacts to n-type SiC, while grains with a high Al concentration correspond to ohmic contacts to p-type SiC. 相似文献
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通过化学气相沉积法,采用不同生长工艺在4°偏角4H-SiC衬底上制备p型4H-SiC同质外延片。提出了p型4H-SiC同质外延中有效层厚度的概念,研究发现导致外延有效层厚度减少的直接原因是自掺杂效应的存在。采用傅里叶红外光谱仪(FT-IR)、汞探针电容电压(Hg-CV)和表面缺陷测试仪对p型4H-SiC同质外延片进行表征,讨论了不同工艺对外延有效层厚度的影响。结果表明,采用隔离法和阻挡层法均能提高外延有效层厚度,且掺杂浓度随距表面深度变化斜率值由1.323减小到0.073。然而,阻挡层法斜率值能进一步优化至0.050,是由于有效抑制了外延中固相和气相自掺杂。对比于优化前工艺,采用阻挡层法制备的p型4H-SiC同质外延片厚度不均匀性和表面总缺陷数量处于同一水平,掺杂浓度不均匀性由2.95%改善到2.67%。综上,采用阻挡层法能够制备出高有效层厚度、高一致性和高质量的p型4H-SiC同质外延片。 相似文献
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级联拉曼激光器的二阶近似解 总被引:1,自引:0,他引:1
利用非线性方法可以得到级联掺磷拉曼光纤激光器的二阶近似解.将描述抽运光和斯托克斯(Stokes)光沿光纤分布的微分方程组简化成代数方程组,在此基础上对抽运光采用二阶非线性近似得到了不同输入抽运功率情况下的近似解,并求出了在二阶非线性近似下的一级Stokes光和二级Stokes光的阈值表达式.利用得到的二阶近似解同一般的数值解法作比较,结果表明两者吻合得很好.一方面,对于双波长输出的级联掺磷拉曼光纤激光器,二阶方法比线性方法更加精确,更接近于一般的数值解;另一方面,该方法有效提高了数值运算速度,优于一般的数值方法. 相似文献
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Raman spectra of undoped GaN and Mg-doped GaN films grown by metal-organic chemical-vapor deposition on sapphire are investigated between 78 and 573K.A peak at 247cm-1 is observed in both Raman spectra of GaN and Mg-doped GaN.It is suggested that the defect-induced scattering is origin of the mode.The electronic Raman scattering mechanism and Mgrelated local vibrational mode are excluded.Furthermore,the differences of E2 and A1(LO) modes in two samples are also discussed.The stress relaxation is observed in Mg-doped GaN. 相似文献
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采用二维器件模拟器ISE TCAD 7.0,对比研究了6H-SiC和4H-SiC VDMOS的基本特性.结果表明,在Vgs为8 V时,4H-SiC VDMOS的漏极电流比6H-SiC高约1.5倍,证实了4H-SiC具有较高的体迁移率,且受准饱和效应的影响较小,因此比6H-SiC器件具有更高的饱和电流密度,而两种器件的阈值电压基本相同,均为7 V左右.对器件开关时间和单位面积损耗的分析表明,4H-SiC比6H-SiC更适合用于VDMOS功率器件.此外,还研究了沟道长度对器件漏极饱和电流的影响,结果表明,随着沟道长度的减小,器件的漏极电流增大. 相似文献
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用倍频Nd:YAG锁模激光532nm泵浦CCl4的背向受激喇曼散射,一阶斯托克斯谱线546nm的能量转移效率为13%,脉宽(FWHM)为8PS,比泵浦激光532nm的脉宽40PS明显变窄。 相似文献