Leakage Current Density-electric Field Research Articles

Effects of Varying Annealing Ambient towards Performance of Ternary GaxCeyOz Passivation Layers for Metal-Oxide-Semiconductor Capacitor

In this work, different annealing ambient (nitrogen-oxygen-nitrogen (N2-O2-N2), forming gas-oxygen-forming gas (FG-O2-FG), and argon-oxygen-argon (Ar-O2-Ar)) were explored to investigate the feasibility of employing the annealed ternary GaxCeyOz passivation layer (PL) for development of Si-based metal-oxide-semiconductor (MOS) capacitors. The impact of nitrogen and/or hydrogen in hindering the growth of silicon dioxide (SiO2) interfacial layer (IL) was quantitatively evaluated. The combination of effects brought by nitrogen attached to oxygen vacancies, nitrogen-silicon bonding, and nitrogen accumulation at the GaxCeyOz/Si interface effectively minimized the formation of SiO2 IL. Consequently, among all the samples, the GaxCeyOz PL annealed in N2-O2-N2 ambient exhibited superior MOS characteristics in terms of low effective oxide charge, slow trap density, interface trap density, and interface state density, which have translated into good leakage current density-electric field characteristics.

Growth of gallium cerium oxide passivation layer on 4H-Silicon carbide substrate and its metal-oxide-semiconductor characteristics

Gallium cerium oxide (GaxCeyOz) passivation layer was successfully grown on 4H-silicon carbide (SiC) through postdeposition annealing at 800 °C in nitrogen-oxygen-nitrogen (N2–O2–N2) ambient. The gracing incident X-ray diffraction and ultraviolet–visible spectrophotometer measurements have confirmed the successful incorporation of Ga3+ cation into the CeO2 lattice to form the ternary GaxCeyOz passivation layer. In addition, the thicknesses of GaxCeyOz passivation layer and silicon dioxide (SiO2) interfacial layer (IL) were determined using field-emission scanning electron microscopy and X-ray reflectivity characterizations. A high dielectric constant (k) value of 24.11 was attained for the investigated Al/GaxCeyOz/4H–SiC/Al metal-oxide-semiconductor (MOS) structure attributable to the nitrogen ions accumulating at the interface that have retarded the growth of SiO2 IL. Besides, the effective oxide charge, slow trap density, interface trap density, interface state density, as well as leakage current density-electric field characteristic of the investigated GaxCeyOz passivation layer on 4H–SiC substrate was presented in this work.

Self-assembly and electrical characteristics of 4-pentynoic acid functionalized Fe3O4-γ-Fe2O3 nanoparticles on SiO2/n-Si

A novel investigation on a relationship between temperature-influential self-assembly (70–300°C) of 4-pentynoic acid functionalized Fe3O4-γ-Fe2O3 nanoparticles (NPs) on SiO2/n-Si with electrical properties was reported with the interests for metal-oxide-semiconductor applications. X-ray diffractometer (XRD) analysis conveyed that 8±1nm of the NPs were assembled. Increasing heating temperature induced growth of native oxide (SiO2). Raman analysis confirmed the coexistence of Fe3O4-γ-Fe2O3. Attenuated Total Reflectance Infrared (ATR-IR) spectra showed that self-assembly occurred via SiOC linkages. While SiOC linkages were broken down at elevated temperatures, formations of Si-OH defects were amplified; a consequence of physisorbed surfactants disintegration. Atomic force microscopy (AFM) showed that sample with more physisorbed surfactants exhibited the highest root-mean-square (RMS) roughness (18.12±7.13nm) whereas sample with lesser physisorbed surfactants displayed otherwise (12.99±4.39nm RMS roughness). Field Emission Scanning Electron Microscope (FE-SEM) analysis showed non-uniform aggregation of the NPs, deposited as film (12.6μm thickness). The increased saturation magnetization (71.527Am2/kg) and coercivity (929.942A/m) acquired by vibrating sample magnetometer (VSM) of the sample heated at 300°C verified the surfactants’ disintegration. Leakage current density-electric field (J-E) characteristics showed that sample heated at 150°C with the most aggregated NPs as well as the most developed SiOC linkages demonstrated the highest breakdown field and barrier height at 2.58×10−3 MV/cm and 0.38eV respectively. Whereas sample heated at 300°C with the least SiOC linkages as well as lesser aggregated NPs showed the lowest breakdown field and barrier height at 1.08×10−3 MV/cm and 0.19eV respectively. This study opens up better understandings on how formation and breaking down of covalent linkages as well as accumulation of defects, particularly prior temperature influential self-assembly at the interfaces, affected electrical breakdown field and barrier height. Hence, possible future development of self-assembly silicon-based metal-oxide-semiconductor (MOS) structure particularly in the presence of SiO2 can be deliberated.

Ultra-high thermal stability and extremely low Dit on HfO2/p-GaAs(001) interface

Molecular beam epitaxy (MBE) HfO2 films ~1.5nm thick were directly deposited on freshly grown GaAs(001)-4×6 reconstructed surfaces. The hetero-structure exhibits outstanding thermal stability up to 900°C with excellent capacitance-voltage (C-V) and leakage current density-electric field (J-E) characteristics. We have extracted low interfacial trap densities (Dit's) with minimum value of 1.3×1011 eV−1cm−2 from the measured quasi-static C-V (QSCV) characteristics. The smallest frequency dispersion of the C-Vs for the MBE-HfO2/p-GaAs(001) is ~5.2% at frequency range of 500 to 1MHz and no trap-induced humps were observed in the C-Vs, as measured at 100°C and 150°C. Also, the leakage current density remains low of 10−8(A/cm2) at E<±3 (MV/cm). The key to passivate GaAs in attaining low Dit's and high-temperature thermal stability is to ensure the cleanness of GaAs surface prior to the high-κ deposition.

Effects of anodization duration on the properties of sputtered samarium thin films on silicon substrate

Sm2O3 was formed by anodization of sputtered Sm thin film on Si substrate at 20 V for different durations (10–25 min). In this study, Sm2O3 thin film formed at anodisation duration of 10 min exhibited the best electrical properties with smallest Qeff value (2.78 × 1023 cm−2), lowest STD (2.91 × 1022 cm−2), minimum Dtotal value (1.98 × 1024 cm−2) and κ-value of 1.33 in capacitance–voltage (C–V) measurement. From leakage current density electric field (J–E) measurement, Sm2O3 thin film formed at anodisation duration of 10 min consisted of two breakdowns, whereby the first breakdown was 3.48 MV/cm at 10−5 A/cm2 and the second breakdown was 9.39 MV/cm at 10−4 A/cm2. This sample showed the highest breakdown electric field among all the samples. This type of oxide may be served as possible candidate as gate dielectric in metal–oxide–semiconductor-based devices.

Characterization of ultrathin Al2O3 gate oxide deposited by RF-magnetron sputtering on gallium nitride epilayer on sapphire substrate

A systematic study was performed on Al2O3 films RF-magnetron sputtered on GaN substrate and subjected to different post-deposition annealing (PDA) temperatures (200–800 °C) in oxygen ambient. The as-deposited Al2O3 film and Al2O3 films subjected to PDA at 200 and 400 °C were present in amorphous phase and therefore undetectable by X-ray diffraction. By further enhancing the PDA temperature (≥600 °C), a transformation from amorphous to polycrystalline phase of Al2O3 happened. The increment of PDA temperature has contributed to an enhancement in leakage current density-electric field (J–E) characteristics of the investigated samples. A correlation between the acquired J–E characteristics with effective oxide charge, slow trap density, interface trap density, and total interface trap density were discussed. A detailed investigation on the conduction of charges through the as-deposited Al2O3 gate and Al2O3 gates subjected to different PDA temperatures via space-charge-limited conduction, Schottky emission, Poole–Frenkel emission, and Fowler–Nordheim tunneling were presented.

Field-dependent charge trapping analysis of ONO inter-poly dielectrics for NAND flash memory applications

The effect of the operation voltage on the leakage current of SiO2/Si3N4/SiO2 (ONO) stack is investigated which is used for the inter-poly dielectric (IPD) of the floating gate (FG) type NAND flash memory. In this work, the field dependent charge trapping mechanism of ONO stack and the effect of the trapped charges on the electrical characteristics are examined. The leakage current density–electric field (J–E) and the capacitance–voltage (C–V) characteristics are measured for various test samples of ONO stack by varying the voltage sweep ranges. The charge trapping/detrapping mechanisms of ONO stack are observed as the range of the applied sweep voltage is increased and then decreased to a given voltage, which is corresponding to the given electric field. The numbers of trapped and detrapped charges are extracted from the difference of J–E curves using the same recursive voltage sweeps and the effects on the electrical characteristics of ONO stack are demonstrated. Moreover, the dominant trapping layer is also investigated by varying the thickness of ONO stack.

Ferroelectric properties of the organic films of poly(vinylidene fluoride-trifluoroethylene blended with inorganic Pb(Zr, Ti)O3

Precursor films based on poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE) and P(VDF-TrFE) blended with Pb(Zr,Ti)O3 were spin-coated on Si-substrates and subsequently annealed at 170°C. X-ray diffraction studies showed that the amorphous precursor films crystallize to the γ-phase P(VDF-TrFE) without involving the formation of other polymorphs when the P(VDF-TrFE) is blended with Pb(Zr,Ti)O3, resulting in phase mixtures composed of a crystalline γ-phase P(VDF-TrFE) and an amorphous Pb(Zr,Ti)O3. A larger memory window width and higher accumulation capacitance, as well as a lower leakage current density are induced by the blended Pb(Zr,Ti)O3 within the low operating voltage ranges from −3.0 to 3.0V and from −2.0 to 2.0V for 20wt% and 40wt% Pb(Zr,Ti)O3 blending, respectively. These improvements not only in the hysteretic capacitance–voltage characteristics but also in the leakage current density–electric field are directly correlated with the phase mixtures, their volume fraction, dipole moments, and formation of interface layer between the blended film and Si substrate.

Comparison of oxidized/nitrided Zr thin films on Si and SiC substrates

This work utilizes simultaneous thermal oxidation and nitridation technique to transform sputtered Zr to ZrO2 and to Zr-oxynitride thin films on Si and SiC substrates, respectively, in nitrous oxide gas ambient. Various characterization techniques such as X-ray photoelectron spectroscopy, energy-filtered transmission electron spectroscopy, atomic force microscopy, X-ray diffraction, capacitance–voltage measurements, and leakage current density-electric field measurements were carried out to evaluate and compare the structural, chemical, and electrical properties of the films produced on both Si and SiC substrates.

Crystallization and Electrical Characteristics of 0.95 (Na0.5Bi0.5)TiO3-0.05 BaTiO3 Thin Films Under Different Annealing Temperature and Atmosphere

0.95 (Na0.5Bi0.5)TiO3-0.05 BaTiO3 +1 wt% Bi2O3 (NBT-BT3) ceramic is used as target to deposit the NBT-BT3 thin films. The excess 1wt% Bi2O3 is used to compensate the vaporization of Bi2O3 during the sintering and annealing processes. NBT-BT3 thin films are successfully deposited using radio frequency (RF) magnetron sputter method and crystallized subsequently using a conventional furnace annealing (CFA) process. The annealed process is conducted in air and in oxygen atmosphere at temperatures ranging from 600-800 degrees C for 60 min. As compared with the as-deposited NBT-BT3 thin films, the CFA-treated process has improved the grain growth and crystallization. We will show that the annealing atmosphere is the more important parameter to influence the grain growth and crystallization of NBT-BT3 thin films than the annealing temperature. The influences of CFA-treated temperature and atmosphere on the electrical characteristics of NBT-BT3 thin films, including the polarization characteristics (Pr, Ps, and Ec values), the capacitance-voltage (C-V) curves, and the leakage current density-electric field (J-E) curves, are also investigated in this study.

Positive temperature coefficient of resistivity in Pt∕(Ba0.7Sr0.3)TiO3∕YBa2Cu3O7-x capacitors

Pt ∕ ( Ba 0.7 Sr 0.3 ) TiO 3 ( BST ) ∕ YBa 2 Cu 3 O 7 - x ( YBCO ) capacitors were fabricated on (001) LaAlO3 substrates. The leakage current density-electric field characteristics were measured in the temperature range from 20 to 300K. In the electric field region of &amp;gt;0.7MV∕cm for positively biased Pt electrode and &amp;gt;1.4MV∕cm for negatively biased Pt electrode, the leakage current shows space-charge-limited-current behavior from 20 to 250K. Meanwhile a positive temperature coefficient of resistivity (PTCR) in the temperature range from 20 to 150K was observed and attributed to the strong negative temperature dependence of the dielectric constant of BST thin films.

Retention characteristics of V-doped Bi 3.25La 0.75Ti 3O 12 thin film

Bi 3.25La 0.75Ti 3O 12 (BLT) and V-doped BLT (BLTV) thin films are prepared on Pt/Ti/SiO 2/Si substrates by a pulsed laser deposition (PLD) method. Ferroelectric and polarization retention characteristics are investigated by leakage current density–electric field ( J– E) and P– E hysteresis loops. The single phases with Bi-layered perovskite structure are confirmed by XRD. The increase of leakage current of BLT and BLTV films are produced at 100 kV/cm and 160 kV/cm, respectively. The long-time retention dispalys a stretched exponential decay for BLT film while a logarithmic decay for BLTV film. After a retention time of 1×10 5 s, the retention loss of BLT and BLTV films were about 14 and 7% of the initial value measured at t=1 s, respectively. BLTV thin film exhibits a retention-free characteristics. The effect of vanadium doping on the retention properties of BLT film will be discussed in detail.

Effect of excess-Pb on the ferroelectric properties of (Pb1−xLax)Ti1−x/4O3 thin films prepared by metal-organic decomposition process

The (Pb1−xLax)Ti1−x/4O3 (PLT) thin films, possessing good ferroelectric properties were successfully obtained by using metal-organic-decomposition (MOD) process. Stoichiometry of the precursors imposes insignificant change on structure and microstructure of the PLT films, but shows marked effect on the leakage current density-electric field (JL-E) and polarization-electric field (P-E) properties of these PLT films. The best properties obtained for PLT films prepared by the MOD process are: Pr= 12.6 μC/cm2, Ec= 80 kV/cm, JL= 10−5A/cm2 (at 400 kV/cm) and p=0.053 μC/cm2K.