Improved performance of Au nanocrystal nonvolatile memory by N_2-plasma treatment on HfO_2 blocking layer

The N_2-plasma treatment on a HfO_2 blocking layer of Au nanocrystal nonvolatile memory without any post annealing is investigated. The electrical characteristics of the MOS capacitor with structure of Al–Ta N/HfO_2/Si O2/p-Si are also characterized. After N_2-plasma treatment, the nitrogen atoms are incorporated into HfO_2 film and may passivate the oxygen vacancy states. The surface roughness of HfO_2 film can also be reduced. Those improvements of HfO_2 film lead to a smaller hysteresis and lower leakage current density of the MOS capacitor. The N_2-plasma is introduced into Au nanocrystal(NC) nonvolatile memory to treat the HfO_2 blocking layer. For the N_2-plasma treated device, it shows a better retention characteristic and is twice as large in the memory window than that for the no N_2-plasma treated device. It can be concluded that the N_2-plasma treatment method can be applied to future nonvolatile memory applications.     

生长气压对分子束外延β-Ga2O3薄膜特性的影响

本文采用分子束外延技术在具有6°斜切角的c面蓝宝石衬底上外延β-Ga₂O₃薄膜,系统研究了生长气压对薄膜特性的影响。X射线衍射谱和表面形貌分析表明,不同生长气压下所外延的薄膜表面平整,均具有(201)择优取向。并且,其结晶质量和生长速率均随生长气压增大而逐渐提高。通过X射线光电子能谱分析发现,生长气压增大使得氧空位的浓度大幅下降,高价态Ga比例增大,最终使得O/Ga原子数之比接近理想Ga₂O₃材料的化学计量比值。利用Tauc公式和乌尔巴赫带尾模型进行计算,结果表明随着生长气压的增大,样品的光学带隙由4.94 eV增加到5.00 eV,乌尔巴赫能量由0.47 eV下降到0.32 eV,证明了生长气压的增大有利于降低薄膜中的缺陷密度,提高薄膜晶体质量。     

硅基锗薄膜选区外延生长研究

利用超高真空化学气相沉积系统, 基于低温Ge缓冲层和选区外延技术, 在Si/SiO₂图形衬底上选择性外延生长Ge薄膜. 采用X射线衍射、扫描电镜、原子力显微镜、拉曼散射光谱等表征了其晶体质量和应变等参数随图形尺寸的变化规律. 测试结果显示, 位错密度随着图形衬底外延窗口的尺寸减小而减少, Ge层中的张应变随窗口尺寸的增大先增大而后趋于稳定. 其原因是选区外延Ge在图形边界形成了(113)面, 减小了材料系统的应变能, 而单位体积应变能随窗口尺寸的增加而减少; 选区外延厚度为380 nm的Ge薄膜X射线衍射曲线半高宽为678", 表面粗糙度为0.2 nm, 表明选区生长的Ge材料具有良好的晶体质量, 有望应用于Si基光电集成.     

Formation of high-Sn content polycrystalline GeSn films by pulsed laser annealing on co-sputtered amorphous GeSn on Ge substrate

Polycrystalline Ge_(1-x)Sn_x(poly-Ge_(1-x)Sn_x) alloy thin films with high Sn content( 10%) were fabricated by cosputtering amorphous GeSn(a-GeSn) on Ge(100) wafers and subsequently pulsed laser annealing with laser energy density in the range of 250 mJ/cm~2 to 550 mJ/cm~2. High quality poly-crystal Ge_(0.90) Sn_(0.10) and Ge_(0.82) Sn_(0.18) films with average grain sizes of 94 nm and 54 nm were obtained, respectively. Sn segregation at the grain boundaries makes Sn content in the poly-GeSn alloys slightly less than that in the corresponding primary a-GeSn. The crystalline grain size is reduced with the increase of the laser energy density or higher Sn content in the primary a-GeSn films due to the booming of nucleation numbers. The Raman peak shift of Ge-Ge mode in the poly crystalline GeSn can be attributed to Sn substitution, strain,and disorder. The dependence of Raman peak shift of the Ge-Ge mode caused by strain and disorder in GeSn films on full-width at half-maximum(FWHM) is well quantified by a linear relationship, which provides an effective method to evaluate the quality of poly-Ge_(1-x)Sn_x by Raman spectra.     

Any-polar resistive switching behavior in Ti-intercalated Pt/Ti/HfO2/Ti/Pt device

The special any-polar resistive switching mode includes the coexistence and stable conversion between the unipolar and the bipolar resistive switching mode under the same compliance current. In the present work, the any-polar resistive switching mode is demonstrated when thin Ti intercalations are introduced into both sides of Pt/HfO₂/Pt RRAM device. The role of the Ti intercalations contributes to the fulfillment of the any-polar resistive switching working mechanism, which lies in the filament constructed by the oxygen vacancies and the effective storage of the oxygen ion at both sides of the electrode interface.     

High-performance germanium n~+/p junction by nickel-induced dopant activation of implanted phosphorus at low temperature

High-performance Ge n~+/p junctions were fabricated at a low formation temperature from 325℃ to 400℃ with a metal(nickel)-induced dopant activation technique. The obtained Ni Ge electroded Ge n+/p junction has a rectification ratio of 5.6×10~4 and a forward current of 387 A/cm~2at -1 V bias. The Ni-based metal-induced dopant activation technique is expected to meet the requirement of the shallow junction of Ge MOSFET.     

简并态锗在大注入下的自发辐射谱模拟

基于费米狄拉克模型模拟了应变、温度以及掺杂对简并态锗的直接带自发辐射谱的影响.随着温度升高,更多的电子被激发到导带中,使得锗自发辐射谱的峰值强度和积分强度随温度的升高而增大.对自发辐射谱峰值强度的m因子进行计算,结果表明张应变可以显著提高锗自发辐射的温度稳定性.在相同应变水平下,由Γ-hh跃迁引起的自发辐射谱峰值强度大于Γ-lh跃迁引起的自发辐射谱峰值强度,但二者的积分强度几乎相等.此外,计算结果还证明了n型掺杂能显著提高锗的自发辐射强度.以上结果对于研究简并态半导体的自发辐射性质有重要的参考意义.