A STUDY OF THE COMPOSITION DISTRIBUTION AT THE TI/AL2O3 INTERFACE USING THE MCS(+)-SIMS TECHNIQUE

In this article, the MCs(+)-SIMS technique has been used to characterize Ti/Al2O3 metal/insulator interfaces. Our experiment shows that by detecting MCs(+) secondary ions, the matrix and interface effects are reduced, and good depth profiles have been obtained. The experimental result also shows that with the increase of the annealing temperature (RT, 300 degrees C, 600 degrees C, 850 degrees C), the interface gets broadened gradually, indicating diffusion and reaction take place at the interface, and the interface reaction is enhanced with the increase in annealing temperature. When the temperature increases, the AlCs+ signal forms two plateaus in the Ti layer, indicating Al from the decomposition of Al2O3 diffuses into the Ti layer and exists as two new forms (phases). Also, with the increase of the annealing temperature, oxygen diffuses into the Ti layer gradually, and makes the O signal in the Ti layer increase significantly in the 850 degrees C annealed sample.

COMPARISON OF PROPERTIES OF SOLID-PHASE EPITAXIAL SILICON-ON-SAPPHIRE FILMS RECRYSTALLIZED BY RAPID THERMAL ANNEALING AND FURNACE ANNEALING

Chemically vapour deposited silicon on sapphire (SOS) films 0.25 mu m thick were implanted with Si-28(+) and recrystallized in solid phase by furnace annealing (FA) and IR rapid thermal annealing (RTA) in our laboratory. An improvement in crystalline quality can be obtained using both annealing procedures. After FA, it is hard to retain the intrinsic high resistivity value(10(4)-10(5) Ohm cm) observed in as-grown SOS films, so the improvement process cannot be put to practical use effectively. However, it is demonstrated that by properly adjusting the implantation and RTA conditions, significant improvements in both film quality and film autodoping can be accomplished. This work describes a modified double solid phase epitaxy process in which the intrinsic high resistivities of the as grown SOS films are retained. The mechanism of suppression of Al autodoping is discussed.

Dislocation Reduction in GaN on Sapphire by Epitaxial Lateral Overgrowth

High quality GaN is grown on GaN substrate with stripe pattern by metalorganic chemical vapor deposition by means of epitaxial lateral overgrowth. AFM,wet chemical etching, and TEM experiments show that with a two-step ELOG procedure, the propagation of defects under the mask is blocked, and the coherently grown GaN above the window also experiences a drastic reduction in defect density. In addition, a grain boundary is formed at the coalescence boundary of neighboring growth fronts. The extremely low density of threading dislocations within wing regions makes ELOG GaN a potential template for the fabrication of nitride-based lasers with improved performance.

X-Band GaN Power HEMTs with Power Density of 2.23W/mm Grown on Sapphire by MOCVD

The growth,fabrication,and characterization of 0.2μm gate-length AlGaN/GaN HEMTs,with a high mobility GaN thin layer as a channel,grown on (0001) sapphire substrates by MOCVD,are described.The unintentionally doped 2.5μm thick GaN epilayers grown with the same conditions as the GaN channel have a room temperature electron mobility of 741cm2/(V·s) at an electron concentration of 1.52×1016 cm-3.The resistivity of the thick GaN buffer layer is greater than 108Ω·cm at room temperature.The 50mm HEMT wafers grown on sapphire substrates show an average sheet resistance of 440.9Ω/□ with uniformity better than 96%.Devices of 0.2μm×40μm gate periphery exhibit a maximum extrinsic transconductance of 250mS/mm and a current gain cutoff frequency of77GHz.The AlGaN/GaN HEMTs with 0.8mm gate width display a total output power of 1.78W (2.23W/mm) and a linear gain of 13.3dB at 8GHz.The power devices also show a saturated current density as high as 1.07A/mm at a gate bias of 0.5V.

Homoepitaxial Growth of 4H-SiC and Ti/4H-SiC SBDs

Homoepitaxial growth of4H-SiC on off-oriented Si-face （0001） 4H-SiC substrates was performed at 1500℃ by using the step controlled Epitaxy. Ti/4H-SiC Schottky barrier diodes （SBDs） with blocking voltage over lkV have been made on an undoped epilayer with 32μm in thick and 2-5 × 10^15 cm^-3 in carrier density. The diode rectification ratio of forward to reverse （defined at ± 1V） is over 107 at room temperature and over 10^2 at 538K. Their electrical characteristics were studied by the current-voltage measurements in the temperature range from 20 to 265 ℃. The ideality factor and Schottky barrier height obtained at room temperature are 1.33 and 0. 905eV, respectively. The SBDs have on-state current density of 150A/cm^2 at a forward voltage drop of about 2.0V. The specific on-resistance for the rectifier is found to be as 7.9mΩ · cm^2 and its variation with temperature is T^2.0.

800nm Semiconductor Absorber with Low Temperature Method and Surface State Method Combined Absorber for Kerr Lens Modelocking of Ti∶Al2O3 Laser

A novel 800nm Bragg mirror type of semiconductor saturable absorption mirror with low temperature method and surface state method combined absorber is presented.With which passive Kerr lens mode locking of Ti∶Al2O3 laser pumped by argon ion laser is realized,which produces pulses as short as 40fs.The spectrum bandwidth is 56nm,which means that it can support the modelocking of 20fs.The pulse frequency is 97.5MHz;average output power is 300mW at the pump power of 4.45W.

Raman Investigatins of 3C-SiC Films Grown on Si (100) and Sapphire (0001) by LPCVD

The Raman measurements have been performed with the back-scattering geometry on the SiC films grown on Si(100) and sapphire (0001) by LPCVD. Typical TO and LO phonon peaks of 3C-SiC were observed for all the samples grown on Si and apphire substrates, indicating the epilayers are 3C-SiC polytype. Using a free-standing 3C-SiC film removed from Si(100) as a free-stress sample, the stresses of 3C-SiC on Si(100) and sapphire (0001) were estimated according to the shift of TO and LO phonons.

高压 Ti/ 6H- SiC肖特基势垒二极管（英文）

在N型6H-SiC外延片上，通过热蒸发，制作Ti/6H-SiC肖特基势垒二极管(SBD)。通过化学气相淀积，进行同质外延生长，详细测量并分析了肖特基二极管的电学特性，该肖特基二极管具有较好的整流特性。反向击穿电压约为400V，室温下，反向电压V_R=200V时，反向漏电流J_R低于1×10~(-4)A/cm~2。采用Ne离子注入形成非晶层，作为边缘终端，二极管的击穿电压增加到约为800V。

Ti-AlN快速退火的界面

国家自然科学基金

Ti/莫来石陶瓷界面反应的俄歇电子能谱研究

结果表明，在淀积过程中，最初淀积的Ti与衬底表面的氧形成Ti-O键，界面区很窄；450℃退火1h后，有少量元素态Al、Si原子析出，界面区有所展宽，但变化不大；650℃退火1h后，界面发生强烈反应，有TiO和Ti-Al、Ti-Si化合物生成。850℃退火1h后，除上述反应产物外又生成了Ti_2O。

Ti薄膜与AlN陶瓷的界面反应

用X射线衍射分析、二次离子质谱、卢瑟福背散射谱、俄歇电子能谱等表面分析技术，研究了Ti膜与AlN陶瓷衬底的界面固相反应。在高真空中用电子束蒸发的方法在抛光的200℃AlN陶瓷衬底上淀积200nm的Ti膜，并在真空恒温炉中退火。实验表明，退火中Ti膜与AlN界面发生了扩散与反应。650℃，1h退火已观测到明显的界面反应。界面反应产物主要是钛铝化物及Ti-N化合物。铝化物是Ti-Al二元化合物和Ti-Al-N三元化合物，850℃,4h退火后则主要由Ti_2AlN组成。

Ti和AlN陶瓷的界面反应

采用电子束蒸发的方法在抛光的200℃AlN陶瓷衬底上淀积厚度为200nm的Ti膜，并在高真空中退火。研究了从200￣850℃温区内Ti与AlN的固相界面反应，给出了界面组分分布随退火温度和时间的变化关系。在界面区发生了三元铝化物并观测到铝化物产生与发展过程。

Ti和蓝宝石的界面反应

在超高真空中用电子束蒸发在抛光的(1102)取向的蓝宝石(a-Al_2O_3)衬底上蒸镀500 nm的Ti膜,在恒温炉中退火,然后用XRD(包括一般的和小角度的X射线衍射),AES和SIMS等表面分析技术详细研究了从室温至850℃,Ti与a-Al_2O_3的固相界面反应.首次系统提出了不同反应温区相应的化学反应式,讨论了采用体材料数据作热力学计算来预言Ti/a-Al_2O_3界面反应的局限性.

Ti Schottky barrier diodes on n-type 6H-SiC

Using thermal evaporation, Ti/6H-SiC Schottky barrier diodes (SBD) were fabricated. They showed good rectification characteristics from room temperature to 200degreesC. At low current density. the current conduction mechanism follows the thermionic emission theory. These diodes demonstrated a low reverse leakage current of below 1 X 10(-4)Acm(-2). Using neon implantation to form the edge termination, the breakdown voltage was improved to be 800V. In addition. these SBDs showed superior switching characteristics.

In situ doping of 3C-SiC grown on (0001) sapphire substrates by LPCVD

The heteroepitaxial growth of n-type and p-type 3C-SiC on (0001) sapphire substrates has been performed with a supply of SiH4+C2H4+H-2 system by introducing ammonia (NH3) and diborane (B2H6) precursors, respectively, into gas mixtures. Intentionally incorporated nitrogen impurity levels were affected by changing the Si/C ratio within the growth reactor. As an acceptor, boron can be added uniformly into the growing 3C-SiC epilayers. Nitrogen-doped 3C-SiC epilayers were n-type conduction, and boron-doped epilayers were p-type and probably heavily compensated.