Interfacial and electrical properties of HfAlO/GaSb metal-oxide-semiconductor capacitors with sulfur passivation

Interfacial and electrical properties of HfAlO/GaSb metal-oxide-semiconductor capacitors(MOSCAPs) with sulfur passivation were investigated and the chemical mechanisms of the sulfur passivation process were carefully studied. It was shown that the sulfur passivation treatment could reduce the interface trap density Ditof the HfAlO/GaSb interface by 35% and reduce the equivalent oxide thickness(EOT) from 8 nm to 4 nm. The improved properties are due to the removal of the native oxide layer, as was proven by x-ray photoelectron spectroscopy measurements and high-resolution cross-sectional transmission electron microscopy(HRXTEM) results. It was also found that GaSb-based MOSCAPs with HfAlO gate dielectrics have interfacial properties superior to those using HfO2 or Al2O3 dielectric layers.     

Research of Trap and Electron Density Distributions in the Interface of Polyimide/Al_2O_3 Nanocomposite Films Based on IDC and SAXS

The distributions of traps and electron density in the interfaces between polyimide(PI) matrix and Al_2O_3 nanoparticles are researched using the isothermal decay current and the small-angle x-ray scattering(SAXS) tests.According to the electron density distribution for quasi two-phase mixture doped by spherical nanoparticles, the electron densities in the interfaces of PI/Al_2O_3 nanocomposite films are evaluated. The trap level density and carrier mobility in the interface are studied. The experimental results show that the distribution and the change rate of the electron density in the three layers of interface are different, indicating different trap distributions in the interface layers. There is a maximum trap level density in the second layer, where the maximum trap level density for the nanocomposite film doped by 25 wt% is 1.054×10~(22) eV·m~(-3) at 1.324 eV, resulting in the carrier mobility reducing. In addition, both the thickness and the electron density of the nanocomposite film interface increase with the addition of the doped Al_2O_3 contents. Through the study on the trap level distribution in the interface, it is possible to further analyze the insulation mechanism and to improve the performance of nano-dielectric materials.     

Study on hydrogen sulfide 790-nm laser diode plasma passivation of cavity surface

In order to improve the optical properties of the Ⅲ-Ⅴ laser diodes （LDs） by means of H2S plasma passivation technology, H2S plasma passivation treatment is performed on the GaAs（110） surface. The optimum passivation conditions obtained are 60-W radio frequency （RF） power and 20-min duration. So the laser cavity surfaces are treated under the optimum passivation conditions. Consequently, compared with unpassivated lasers with only AR/HR-eoatings, the catastrophic optical damage （COD） threshold value of the passivated lasers by H2S plasma treatment is increased by 33%, which is almost the same as that of （NH4）2Sx treatment. And the life-test experiment has demonstrated that this passivation method is more stable than （NH4）2Sx solution wet-passivated treatment.     

AlGaN/GaN high electron mobility transistor with Al_2O_3+BCB passivation

In this paper, A12O3 ultrathin film used as the surface passivation layer for Al Ga N/Ga N high electron mobility transistor(HEMT) is deposited by thermal atomic layer deposition(ALD), thereby avoiding plasma-induced damage and erosion to the surface. A comparison is made between the surface passivation in this paper and the conventional plasma enhanced chemical vapor deposition(PECVD) Si N passivation. A remarkable reduction of the gate leakage current and a significant increase in small signal radio frequency(RF) performance are achieved after applying Al2O3+BCB passivation.For the Al2O3+BCB passivated device with a 0.7 μm gate, the value of f max reaches up to 100 GHz, but it decreases to 40 GHz for Si N HEMT. The f max/ f t ratio(≥ 4) is also improved after Al2O3+BCB passivation. The capacitance–voltage(C–V) measurement demonstrates that Al2O3+BCB HEMT shows quite less density of trap states(on the order of magnitude of 1010cm-2) than that obtained at commonly studied Si N HEMT.     

Interfacial and electrical properties of HfAIO/GaSb metal-oxide-semiconductor capacitors with sulfur passivation Interfacial and electrical properties of HfAIO/GaSb metal-oxide-semiconductor capacitors with sulfur passivation Interfacial and electrical properties of HfAIO/GaSb metal-oxide-semiconductor capacitors with sulfur passivationInterfacial and electrical properties of HfAIO/GaSb metal-oxide-semiconductor capacitors with sulfur passivation

Interfacial and electrical properties of HfA10/GaSb metal-oxide-semiconductor capacitors （MOSCAPs） with sulfur passivation were investigated and the chemical mechanisms of the sulfur passivation process were carefully studied. It was shown that the sulfur passivation treatment could reduce the interface trap density Dit of the HfAIO/GaSb interface by 35% and reduce the equivalent oxide thickness （EOT） from 8 nm to 4 nm. The improved properties are due to the removal of the native oxide layer, as was proven by x-ray photoelectron spectroscopy measurements and high-resolution cross-sectional transmission electron microscopy （HRXTEM） results. It was also found that GaSb-based MOSCAPs with HfA10 gate dielectrics have interfacial properties superior to those using HfO2 or A1203 dielectric layers.     

High-Density Stacked Ru Nanocrystals for Nonvolatile Memory Application

Stacked ruthenium （Ru） nanocrystals （NCs） are formed by rapid thermal annealing for the whole gate stacks and embedded in memory structure, which is compatible with conventional CMOS technology. Ru NCs with high density （3 × 10^12 cm-2）, small size （2 4nm） and good uniformity both in aerial distribution and morphology are formed. Attributed to the higher surface trap density, a memory window of 5.2 V is obtained with stacked Ru NCs in comparison to that of 3.5 V with single-layer samples. The stacked Ru NCs device also exhibits much better retention performance because of Coulomb blockade and vertical uniformity between stacked Ru NCs.     

THERMOELECTRIC POWER IN (Gd,Sm)1.85Ce0.15CuO4 SYSTEM

Thermoelectric power measurements are reported for seven samples with different x in the Gd_1.85-xSm_xCe_0.15CuO₄ system at temperatures ranging from 80K to 300K. For Sm-rich superconducting samples, thermoelectric power S has a small negative value and is almost temperature independent. As the content of Sm decreases, the absolute value of S increases and a broad valley appears in the S(T) curve. The results which can be interpreted in terms of a two-channel model support the existence of mid-gap states with Fermi level close to the minimum of the density of states as well as the coexistence of electron and hole carriers. It is suggested that a linear temperature dependence of S with a small negative slope is close to the intrinsic behavior in the a-b plane of normal states for superconducting samples.     

Numerical investigations on the current conduction in bilayer organic light-emitting devices with ohmic injection of charge carriers

A numerical model for bilayer organic light-emitting diodes (OLEDs) has been developed on the basis of trapped charge limited conduction. The dependences of the current density on the operation voltage, the thickness and trap properties of the hole transport layer (HTL) and emission layer (EML) in bilayer OLEDs of the structure anode/HTL/EML/cathode have been numerically investigated. It has been found that, for given values of reduced trap depth, total trap density, and cv~rrier mobility of HTL and EML, there exists an optimum thickness ratio of HTL to the sum of HTL and EML, by which a maximal current density, and hence maximal quantum efficiency and luminance,can be achieved. The current density decreases quickly with the mean trap density, and decreases nearly exponentially with the mean reduced trap depth.     

Study on hydrogen sulfide plasma passivation of 790-nm laser diode cavity surface

In order to improve the optical properties of theⅢ-Ⅴlaser diodes(LDs)by means of H_2S plasma passiva- tion technology,H_2S plasma passivation treatment is performed on the GaAs(110)surface.The optimum passivation conditions obtained are 60-W radio frequency(RF)power and 20-min duration.So the laser cavity surfaces are treated under the optimum passivation conditions.Consequently,compared with un- passivated lasers with only AR/HR-coatings,the catastrophic optical damage(COD)threshold value of the passivated lasers by H_2S plasma treatment is increased by 33%,which is almost the same as that of (NH_4)_2S_x treatment.And the life-test experiment has demonstrated that this passivation method is more stable than(NH_4)_2S_x solution wet-passivated treatment.     

Simulation and Optimization of Miniature Ring-Endcap Ion Traps

With the decrease in dimension of ion traps employed in optical frequency standards and precision spectroscopy, the sensitivity of trapping behavior to trap geometry is more and more prominent. We present a guide for the design and construction of a miniature trap for a single ion confinement, and propose an optimized combination of Tring/Tendcap ≈0.5 and z0≈ ro within the range of To = 0.7 ± 0.2 mm. Compared with the trap used by Huang et al. [Phys. Rev. A 84 （2011）053841], the design can lead to an increase in trap pseudo-potentiM of more than 20% and a reduction on potential anharmonicity of more than 90%. The improvements make the trap closer to an ideal hyperboloidal trap to confine a single ion tightly with the benefit of weaker micro-motion. Considering the imperfection of electrodes machining and traps Mignment, we also demonstrate the importance of trap symmetry, especially on two endcap electrodes.     

多种含硫溶液钝化(100)GaAs表面的实验研究

为实现GaAs表面的钝化,以Na2S、(NH4)2S、CH3CSNH2为主要研究对象,通过对比实验研究得出较为理想的湿法钝化液。通过光致发光(PL)谱研究了(NH4)2S 叔丁醇、CH3CSNH2 NH4OH、CH3CSNH2 叔丁醇三种不同含硫溶液钝化(100)GaAs表面后的发光特性。PL谱测试发现,(NH4)2S 叔丁醇饱和溶液处理过的(100)GaAs表面光致发光强度最强,PL谱的相对发光强度是未做钝化处理的10倍左右。因此得出(NH4)2S 叔丁醇饱和溶液是较为理想的(100)GaAs表面钝化液。     

Study on hydrogen sulfide plasma passivation of 790-nm laser diode cavity surface

In order to improve the optical properties of the Ⅲ-Ⅴ laser diodes(LDs) by means of H2S plasma passivation technology,H2S plasma passivation treatment is performed on the GaAs(110) surface.The optimum passivation conditions obtained are 60-W radio frequency(RF)power and 20-min duration.So the laser cavity surfaces axe treated under the optimum passivation conditions.Consequently,compared with unpassivated lasers with only AR/HR-coatings,the catastrophic optical damage (COD) threshold value of the passivated lasers by H2S plasma treatment is increased by 33%,which is almost the same as that of (NH4)2Sx treatment.And the life-test experiment has demonstrated that this passivation method is more stable than(NH4)2Sx solution wet-passivated treatment.     

聚合物PVP表面修饰CdS纳米棒的制备及其光谱特性

用水热合成方法制备了PVP表面修饰CdS纳米棒,用XRD,TEM,TG-DTA,IR,UV-Vis,PL等光谱技术进行了表征。与未修饰的CdS纳米棒相比,PVP修饰后的CdS纳米棒具有更均匀的尺寸分布,吸收光谱具有结构峰特征,其荧光发射谱增强。     

H,Cl和F原子钝化Cu_2ZnSnS_4(112)表面态的第一性原理计算

采用基于密度泛函理论的第一性原理计算方法系统研究了Cu_2ZnSnS_4体相的晶格结构、能带、态密度及表面重构与H,Cl和F原子在Cu_2ZnSnS_4(112)表面上的吸附和钝化机理.计算结果表明:表面重构出现在以金属原子Cu-Zn-Sn终止的Cu_2ZnSnS_4(112)表面上,并且表面重构使表面发生自钝化;当单个H,Cl或F原子吸附在S原子终止的Cu_2ZnSnS_4(112)表面上时,相比于桥位(bridge)、六方密排(hcp)位和面心立方(fcc)位点,三种原子均在特定的顶位(top)吸附位点表现出最佳稳定性.当覆盖度为0.5 ML时,无论H,Cl还是F原子占据Cu_2ZnSnS_4(112)表面的2个顶位均具有最低的吸附能.以S原子终止的Cu_2ZnSnS_4(112)表面在费米能级附近的电子态主要由价带顶部Cu-3d轨道和S-3p轨道电子贡献,此即表面态.当H,Cl或F原子在表面的覆盖度达0.5 ML时,费米能级附近的表面态降低,其中H原子钝化表面态的效果最佳,Cl原子的效果次之,F原子的效果最差.表面态降低的主要原因在于吸附原子从S原子获得电子致使表面Cu原子和S原子在费米能级处的态密度峰几乎完全消失.     

Effect of SiN:H_x passivation layer on the reverse gate leakage current in GaN HEMTs

This paper concentrates on the impact of SiN passivation layer deposited by plasma-enhanced chemical vapor deposition(PECVD) on the Schottky characteristics in GaN high electron mobility transistors(HEMTs). Three types of SiN layers with different deposition conditions were deposited on GaN HEMTs. Atomic force microscope(AFM), capacitance-voltage(C-V), and Fourier transform infrared(FTIR) measurement were used to analyze the surface morphology, the electrical characterization, and the chemical bonding of SiN thin films, respectively. The better surface morphology was achieved from the device with lower gate leakage current. The fixed positive charge Q_f was extracted from C-V curves of Al/SiN/Si structures and quite different density of trap states(in the order of magnitude of 1011-1012 cm~(-2)) was observed.It was found that the least trap states were in accordance with the lowest gate leakage current. Furthermore, the chemical bonds and the %H in Si-H and N-H were figured from FTIR measurement, demonstrating an increase in the density of Q_f with the increasing %H in N-H. It reveals that the effect of SiN passivation can be improved in GaN-based HEMTs by modulating %H in Si-H and N-H, thus achieving a better Schottky characteristics.     

表面氧钝化碳化硅纳米团簇电子结构和光学性质的第一性原理研究

基于密度泛函理论(DFT)和广义梯度近似(GGA),对氧钝化条件下4H-SiC纳米团簇的电子结构和光学性质进行了研究。计算了不同直径的4H-SiC纳米球氧钝化后的能带结构、电子态密度和光学性质。团簇的尺度在0.4~0.9 nm之间,构建表面仅存在硅氧双键和表面仅存在碳氧双键的两种模型。研究表明硅氧双键和碳氧双键所引起的缺陷态位于原4H-SiC的价带和导带之间,并且缺陷态与价带顶的能量差随纳米团簇颗粒直径的增大而减小;缺陷态主要是由Si原子外层电子和氧原子外层电子轨道杂化引起的。同时,由于氧的存在,对碳化硅的结构产生一定的影响,这也是缺陷态形成的一个原因。另外,碳氧双键和硅氧双键钝化对4H-SiC纳米团簇的光学性质有着不同的影响。在表面仅存在C=O的情况下,4H-SiC纳米团簇表现出各向同性的性质。在表面仅存在Si=O的情况下,4H-SiC纳米团簇表现出各向异性的性质。     

Passivation of TiO2 by ultra-thin Al-oxide

The passivation of sol–gel TiO₂ by ultra-thin layers of Al-oxide has been investigated using transient and spectral photovoltage (PV) techniques. The ultra-thin layers of Al-oxide were prepared by the ion-layer gas reaction (ILGAR) technique and modified by thermal treatments in air, vacuum or Ar/H₂S atmosphere. The samples where characterized by elastic recoil detection analysis (ERDA), X-ray photoelectron spectroscopy (XPS), and contact potential difference (CPD) technique. Without an Al-oxide surface layer, electronic states in the forbidden gap of TiO₂ are formed during thermal treatments in vacuum and Ar/H₂S. The trap density is strongly reduced at the TiO₂/Al-oxide interface. The formation of electronic defects is prevented by a closed ultra-thin layer of Al-oxide.     

Effect of N 2 + ion implantation on the electrochemical corrosion behaviour of Fe−Ni alloy in. 1N H2SO4 solution

A three sweep potentiokinetic technique was employed to study the electrochemical corrosion behaviour of Fe-50 at % Ni in .1N H₂SO₄ solution. The as received foil did not show any passivation but it was observed in case of Fe?Ni samples implanted with N₂ ⁺ ions at an energy of 100keV. Also it was seen that the primary passivation potential E_pp and the critical current density in the corrosion experiment decrease as the implanted nitrogen ion dose increases from 5*10¹⁵ to 1*10¹⁷ ions/cm². The identification of products formed during corrosion experiment has been attempted with the help of conversion electron Mössbauer spectroscopy (CEMS), X-ray diffraction (XRD) and X-ray photoemission spectroscopic (XPS) techniques, and the possible mechanism of reactions is discussed with reference to their results.     

Sulfide passivation of InAs(100) substrates in Na<Subscript>2</Subscript>S solutions

Treatment of the InAs(100) surface with a 1M aqueous solution of sodium sulfide (Na₂S) is found to result in the removal of a natural oxide layer from this surface with the formation of a continuous chemisorbed passivating layer of sulfur atoms that are coherently bonded to indium atoms of the crystal surface. No etching of the InAs surface in the sulfide solution occurs. The passivated InAs samples are characterized by a multiple increase in the photoluminescence intensity. The sulfide layer is desorbed from the InAs surface at temperatures of ～400°C. This leads to the formation of a clean In-stabilized (100) surface with a (4 × 2) reconstruction. A simple technique is developed using sulfide passivation for preparing atomically smooth (2 × 4) growth surfaces of the InAs(100) substrates that are suitable for molecular-beam epitaxy of highly perfect layers of compounds based on CdSe.