Improved Electrical Properties of Ge p-MOSFET With $ hbox{HfO}_{2}$ Gate Dielectric by Using $hbox{TaO}_{x} hbox{N}_{y}$ Interlayer

The electrical characteristics of germanium p-metal-oxide-semiconductor (p-MOS) capacitor and p-MOS field-effect transistor (FET) with a stack gate dielectric of HfO₂/TaOxNy are investigated. Experimental results show that MOS devices exhibit much lower gate leakage current than MOS devices with only HfO₂ as gate dielectric, good interface properties, good transistor characteristics, and about 1.7-fold hole-mobility enhancement as compared with conventional Si p-MOSFETs. These demonstrate that forming an ultrathin passivation layer of TaOxNy on germanium surface prior to deposition of high-k dielectrics can effectively suppress the growth of unstable GeOx, thus reducing interface states and increasing carrier mobility in the inversion channel of Ge-based transistors.     

Improvement of On–Off-Current Ratio in $ hbox{TiO}_{rm x}$ Active-Channel TFTs Using $hbox{N}_{2} hbox{O}$ Plasma Treatment

Without sacrificing the on-current in the transfer characteristics, we have successfully reduced the off-current part by the optimal $hbox{N}_{2}hbox{O}$ plasma treatment to improve the on–off-current ratio in n-type titanium oxide $( hbox{TiO}_{rm x})$ active-channel thin-film transistors. While the high-power (275 W) $hbox{N}_{2}hbox{O}$ plasma treatment oxidizes the whole $hbox{TiO}_{rm x}$ channel and results in the reduction of both on- and off-current, the optimized low-power (150 W) process makes the selective oxidation of the top portion in the channel and reduces only the off-current significantly. Increase in on–off ratio by almost five orders of magnitude is achieved without change in on-current by using the presented method.      

AlGaN/GaN MOSHEMTs With Liquid-Phase-Deposited $ hbox{TiO}_{2}$ as Gate Dielectric

$hbox{TiO}_{2}$ films deposited on GaN layers at room temperature through a simple and low-cost liquid-phase deposition (LPD) method are investigated and served as gate dielectrics in AlGaN/GaN MOSHEMTs. The electrical characteristics of the MOS structure on n-doped GaN show that the leakage current is about $hbox{1.01} times hbox{10}^{-7} hbox{A/cm}^{2}$ at 1 MV/cm and that the breakdown field is more than 6.5 MV/cm. The maximum drain current density of MOSHEMTs is higher than that of conventional HEMTs, and a wider gate voltage swing can also be observed. The maximum transconductance and threshold voltage almost maintain the same characteristics, even after inserting a dielectric layer between the gate metal and the 2DEG channel by using $ hbox{TiO}_{2}$ as a gate dielectric. The gate leakage current density is significantly improved, and the bias stress measurement shows that current collapse is much suppressed for MOSHEMTs.      

High-Performance $hbox{In}_{0.7}hbox{Ga}_{0.3}hbox{As}$ -Channel MOSFETs With High-$kappa$ Gate Dielectrics and $alpha$-Si Passivation

Long and short buried-channel $hbox{In}_{0.7}hbox{Ga}_{0.3}hbox{As}$ MOSFETs with and without $alpha$-Si passivation are demonstrated. Devices with $alpha$-Si passivation show much higher transconductance and an effective peak mobility of 3810 $hbox{cm}^{2}/ hbox{V} cdot hbox{s}$. Short-channel MOSFETs with a gate length of 160 nm display a current of 825 $muhbox{A}/muhbox{m}$ at $V_{g} - V_{t} = hbox{1.6} hbox{V}$ and peak transconductance of 715 $muhbox{S}/muhbox{m}$. In addition, the virtual source velocity extracted from the short-channel devices is 1.4–1.7 times higher than that of Si MOSFETs. These results indicate that the high-performance $hbox{In}_{0.7}hbox{Ga}_{0.3} hbox{As}$-channel MOSFETs passivated by an $alpha$ -Si layer are promising candidates for advanced post-Si CMOS applications.      

A Comparative NBTI Study of $hbox{HfO}_{2}$, $hbox{HfSiO}_{x}$, and SiON p-MOSFETs Using UF-OTF $I_{rm DLIN}$ Technique

The time, temperature, and oxide-field dependence of negative-bias temperature instability is studied in $hbox{HfO}_{2}/hbox{TiN}$, $ hbox{HfSiO}_{x}/hbox{TiN}$, and SiON/poly-Si p-MOSFETs using ultrafast on-the-fly $I_{rm DLIN}$ technique capable of providing measured degradation from very short (approximately microseconds) to long stress time. Similar to rapid thermal nitrided oxide (RTNO) SiON, $hbox{HfO}_{2}$ devices show very high temperature-independent degradation at short (submilliseconds) stress time, not observed for plasma nitrided oxide (PNO) SiON and $hbox{HfSiO}_{x}$ devices. $hbox{HfSiO}_{x}$ shows lower overall degradation, higher long-time power-law exponent, field acceleration, and temperature activation as compared to $hbox{HfO}_{2}$, which are similar to the differences between PNO and RTNO SiON devices, respectively. The difference between $ hbox{HfSiO}_{x}$ and $hbox{HfO}_{2}$ can be attributed to differences in N density in the $hbox{SiO}_{2}$ IL of these devices.      

Optimal $ Sigma Delta$ Modulator Architectures for Fractional-$ {N}$ Frequency Synthesis

This paper presents a comparative study of $Sigma Delta$ modulators for use in fractional-$ {N}$ phase-locked loops. It proposes favorable modulator architectures while taking into consideration not only the quantization noise of the modulator but also other loop nonidealities such as the charge pump current mismatch that contributes to the degradation in the synthesized tone's phase noise. The proper choice of the modulator architecture is found to be dependent upon the extent of the nonideality, reference frequency, and loop bandwidth. Three modulator architectures are then proposed for low, medium, and high levels of nonidealities.      

Impacts of $hbox{N}_{2}$ and $hbox{NH}_{3}$ Plasma Surface Treatments on High-Performance LTPS-TFT With High-$kappa$ Gate Dielectric

Low-temperature polycrystalline-silicon thin-film transistors (LTPS-TFTs) with high- $kappa$ gate dielectrics and plasma surface treatments are demonstrated for the first time. Significant field-effect mobility $mu_{rm FE}$ improvements of $sim$86.0% and 112.5% are observed for LTPS-TFTs with $hbox{HfO}_{2}$ gate dielectric after $hbox{N}_{2}$ and $ hbox{NH}_{3}$ plasma surface treatments, respectively. In addition, the $hbox{N}_{2}$ and $ hbox{NH}_{3}$ plasma surface treatments can also reduce surface roughness scattering to enhance the field-effect mobility $mu_{rm FE}$ at high gate bias voltage $V_{G}$, resulting in 217.0% and 219.6% improvements in driving current, respectively. As a result, high-performance LTPS-TFT with low threshold voltage $V_{rm TH} sim hbox{0.33} hbox{V}$, excellent subthreshold swing S.S. $sim$0.156 V/decade, and high field-effect mobility $mu_{rm FE} sim hbox{62.02} hbox{cm}^{2}/hbox{V} cdot hbox{s}$ would be suitable for the application of system-on-panel.      

Nonvolatile-Memory Characteristics of $hbox{AlO}^{-}$ -Implanted $hbox{Al}_{2}hbox{O}_{3}$

The nonvolatile-memory (NVM) characteristics of $hbox{AlO}^{-}$ -implanted $hbox{Al}_{2}hbox{O}_{3}$ structures are reported and shown to exhibit promising behaviors, including fast program/erase speeds and high-temperature data retention. Photoconductivity spectra show the existence of two dominant trap levels, located at around 2 and 4 eV below the conduction band minimum of $hbox{Al}_{2}hbox{O}_{3}$, and our calculations show that these levels are likely attributed to the defects in the $hbox{Al}_{2}hbox{O}_{3}$, such as the Al–O divacancy. The relative concentrations of these defects vary with the implant fluence and are shown to explain the NVM characteristics of the samples irradiated to different fluences.      

Low-Voltage Organic Field-Effect Transistor With PMMA/$ hbox{ZrO}_{2}$ Bilayer Dielectric

This paper reports on the application of a bilayer polymethylmethacrylate (PMMA)/ $hbox{ZrO}_{2}$ dielectric in copper phthalocyanine (CuPc) organic field-effect transistors (OFETs). By depositing a PMMA layer on $hbox{ZrO}_{2}$, the leakage of the dielectric is reduced by one order of magnitude compared to single-layer $hbox{ZrO}_{2}$. A high-quality interface is obtained between the organic semiconductor and the combined insulators. By integrating the advantages of polymer and high- $k$ dielectrics, the device achieves both high mobility and low threshold voltage. The typical field-effect mobility, threshold voltage, on/off current ratio, and subthreshold slope of OFETs with bilayer dielectric are $hbox{5.6}timeshbox{10}^{-2} hbox{cm}^{2}/hbox{V} cdot hbox{s}$, 0.8 V, $hbox{1.2} times hbox{10}^{3}$, and 2.1 V/dec, respectively. By using the bilayer dielectrics, the hysteresis observed in the devices with single-layer $hbox{ZrO}_{2}$ is no longer present.      

180$^{circ}$ and 90$^{circ}$ Phase Shifting Networks With an Octave Bandwidth and Small Phase Errors

A new phase shifting network for both 180 $^{circ}$ and 90 $^{circ}$ phase shift with small phase errors over an octave bandwidth is presented. The theoretical bandwidth is 67% for the 180$^{circ}$ phase bit and 86% for the 90$^{circ}$ phase bit when phase errors are $pm 2^{circ}$. The proposed topology consists of a bandpass filter (BPF) branch, consisting of a LC resonator and two shunt quarter-wavelength transmission lines (TLs), and a reference TL. A theoretical analysis is provided and scalable parameters are listed for both phase bits. To test the theory, phase shifting networks from 1 GHz to 3 GHz were designed. The measured phase errors of the 180$^{circ}$ and the 90$^{circ}$ phase bit are $pm 3.5^{circ}$ and $pm 2.5^{circ}$ over a bandwidth of 73% and 102% while the return losses are better than 18 dB and 12 dB, respectively.      

New Terahertz Laser Lines From $^{13}{hbox {CD}}_{3}{hbox {OH}}$ Pumped by Regular and Hot Bands ${hbox {CO}}_{2}$ Laser

We have used our new pulsed ${hbox {CO}}_{2}$ laser, operating both on regular and hot bands, to excite the $^{13}{hbox {CD}}_{3}{hbox {OH}}$ methanol isotopomer. This has lead to the observation of 13 new high-threshold far-infrared laser emissions (also identified as terahertz laser lines), with frequencies in the range between 24.11 and 102.56 cm$^{-1}$ (0.72–3.07 THz). The absorption transitions leading to these new FIR laser emissions have been located by observing the optoacoustic absorption spectra around the ${hbox {CO}}_{2}$ emissions. Here, we present these new far-infrared laser lines, characterized in wavelength, polarization, offset relative to the center of the pumping ${hbox {CO}}_{2}$ laser transition, relative intensity, and optimum operation pressure.      

High-Density and Low-Leakage-Current MIM Capacitor Using Stacked $hbox{TiO}_{2}/hbox{ZrO}_{2}$ Insulators

We have fabricated high-$kappa hbox{Ni}/hbox{TiO}_{2}/hbox{ZrO}_{2}/ hbox{TiN}$ metal–insulator–metal (MIM) capacitors. A low leakage current of $hbox{8} times hbox{10}^{-8} hbox{A/cm}^{2}$ at 125 $^{circ}hbox{C}$ was obtained with a high 38- $hbox{fF}/muhbox{m}^{2}$ capacitance density and better than the $hbox{ZrO}_{2}$ MIM capacitors. The excellent device performance is due to the lower electric field in 9.5-nm-thick $hbox{TiO}_{2}/ hbox{ZrO}_{2}$ devices to decrease the leakage current and to a higher $kappa$ value of 58 for $ hbox{TiO}_{2}$ as compared with that of $hbox{ZrO}_{2}$ to preserve the high capacitance density.      

Schottky Barrier Height of Erbium Silicide on $ hbox{Si}_{1 - x}hbox{C}_{x}$

In this letter, the Schottky barrier height of erbium silicide contacts formed on $hbox{Si}_{1 - x}hbox{C}_{x}$ alloys was measured. The alloys were pseudomorphically grown on Si wafers with 0% to 1.2% C occupying the substitutional sites. Schottky barrier diodes were fabricated with an ideality factor of 1.13 or less. The hole barrier height was found to be 0.73 eV independent of the C concentration. This suggests that the electron barrier height should decrease with increasing C concentration due to the reduction in the semiconductor bandgap. For 1.2% C, the electron barrier is estimated to be 0.29 eV.      

Eigendecomposition of Images Correlated on $S^{1}$, $S^{2}$, and $SO(3)$ Using Spectral Theory

Eigendecomposition represents one computationally efficient approach for dealing with object detection and pose estimation, as well as other vision-based problems, and has been applied to sets of correlated images for this purpose. The major drawback in using eigendecomposition is the off line computational expense incurred by computing the desired subspace. This off line expense increases drastically as the number of correlated images becomes large (which is the case when doing fully general 3-D pose estimation). Previous work has shown that for data correlated on S ¹ , Fourier analysis can help reduce the computational burden of this off line expense. This paper presents a method for extending this technique to data correlated on S ² as well as SO(3) by sampling the sphere appropriately. An algorithm is then developed for reducing the off line computational burden associated with computing the eigenspace by exploiting the spectral information of this spherical data set using spherical harmonics and Wigner-D functions. Experimental results are presented to compare the proposed algorithm to the true eigendecomposition, as well as assess the computational savings.     

Gate Influence on the Layout Sensitivity of $ hbox{Si}_{1 - x}hbox{Ge}_{x} hbox{S/D}$ and $hbox{Si}_{1 - y}hbox{C}_{y} hbox{S/D}$ Transistors Including an Analytical Model

We present a simulation study on the effect of the gate module on the channel stress in Si_1-xGe_x and Si_1-yC_y S/D MOS transistors. Stiff gate materials, such as titanium nitride, lead to a decreased channel stress, while a replacement-gate scheme allows the increase of the effectiveness of the Si_1-xGe_x and Si_1-yC_y S/D techniques significantly, independent of the gate material used. The drawback of using a replacement gate is that the channel stress becomes more sensitive to layout variations. In terms of effect on Si_1-xGe_x/Si_1-yC_y S/D stress generation, using a thin metal gate capped by polysilicon is similar to a full metal gate if the thin metal gate thickness exceeds 10 nm. Even metal gates as thin as 1 nm have a clear influence on the stress generation by Si_1-xGe_x/Si_1-yC_y S/D. Removing and redepositing the polysilicon layer while leaving the underlying metal gate unchanged increases the stress, although not to the same extent as for complete gate removal. A simple analytical model that estimates the stress in nested short-channel Si_1-xGe_x and Si_1-yC_y S/D transistors is presented. This model includes the effect of germanium/carbon concentration, active-area length, as well as the effect of gate length and the Young's modulus of the gate. Good qualitative agreement with 2-D finite element modeling is demonstrated.     

Gate-Recessed InAlN/GaN HEMTs on SiC Substrate With $ hbox{Al}_{2}hbox{O}_{3}$ Passivation

We studied submicrometer $(L_{G} = hbox{0.15} {-} hbox{0.25} mu hbox{m})$ gate-recessed InAlN/AlN/GaN high-electron mobility transistors (HEMTs) on SiC substrates with 25-nm $hbox{Al}_{2}hbox{O}_{3}$ passivation. The combination of a low-damage gate-recess technology and the low sheet resistance of the InAlN/AlN/GaN structure resulted in HEMTs with a maximum dc output current density of $I_{{rm DS}, max} = hbox{1.5} hbox{A/mm}$ and a record peak extrinsic transconductance of $g_{m, {rm ext}} = hbox{675} hbox{mS/mm}$. The thin $hbox{Al}_{2}hbox{O}_{3}$ passivation improved the sheet resistance and the transconductance of these devices by 15% and 25%, respectively, at the same time that it effectively suppressed current collapse.      

Pentacene-Based Low-Voltage Strain Sensors With PVP/$ hbox{Ta}_{2}hbox{O}_{5}$ Hybrid Gate Dielectrics

Field-controllable pentacene-semiconductor-based strain sensors were fabricated with hybrid gate dielectrics using polyvinyl phenol (PVP) and high-$k$ inorganic tantalum pentoxide $(hbox{Ta}_{2}hbox{O}_{5})$ onto polyethylene naphthalate films. The $hbox{Ta}_{2}hbox{O}_{5}$ gate-dielectric layer combined with a thin PVP layer to form very smooth and hydrophobic surfaces turns out to improve the molecular structures of pentacene films significantly. The PVP– $hbox{Ta}_{2}hbox{O}_{5}$ hybrid-gate-dielectric films exhibit a high dielectric constant of 19.27 and a leakage-current density of as low as 100 $hbox{nA/cm}^{2}$ . The sensors employing a thin-film-transistor-like Wheatstone bridge configuration able to operate at reduced voltage ($sim$4 V) show good device characteristics with a field-effect mobility of 1.89 $hbox{cm}^{2}/hbox{V} cdot hbox{s}$ and a threshold voltage of $-$0.5 V. The strain sensor characterized with bending at 45$^{circ}$ with respect to the bridge bias direction with different bending radii of 50-, 40-, 30-, 20-, and 8-mm displays output signals improved in linearity in a low range of operating voltages.      

Electrical Properties of Amorphous $hbox{Bi}_{5} hbox{Nb}_{3}hbox{O}_{15}$ Thin Film for RF MIM Capacitors

Amorphous $hbox{Bi}_{5}hbox{Nb}_{3}hbox{O}_{15}(hbox{B}_{5} hbox{N}_{3})$ film grown at 300 $^{circ}hbox{C}$ showed a high-$k$ value of 71 at 100 kHz, and similar $k$ value was observed at 0.5–5.0 GHz. The 80-nm-thick film exhibited a high capacitance density of 7.8 fF/$muhbox{m}^{2}$ and a low dissipation factor of 0.95% at 100 kHz with a low leakage-current density of 1.23 nA/ $hbox{cm}^{2}$ at 1 V. The quadratic and linear voltage coefficient of capacitances of the $hbox{B}_{5}hbox{N}_{3}$ film were 438 ppm/$hbox{V}^{2}$ and 456 ppm/V, respectively, with a low temperature coefficient of capacitance of 309 ppm/$^{circ}hbox{C}$ at 100 kHz. These results confirmed the potential of the amorphous $hbox{B}_{5}hbox{N}_{3}$ film as a good candidate material for a high-performance metal–insulator–metal capacitors.      

AlGaN/GaN MOS-HEMT With $hbox{HfO}_{2}$ Dielectric and $hbox{Al}_{2}hbox{O}_{3}$ Interfacial Passivation Layer Grown by Atomic Layer Deposition

We have developed a novel AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistor using a stack gate HfO₂/Al₂O₃ structure grown by atomic layer deposition. The stack gate consists of a thin HfO₂ (30-A) gate dielectric and a thin Al₂O₃ (20- A) interfacial passivation layer (IPL). For the 50-A stack gate, no measurable C-V hysteresis and a smaller threshold voltage shift were observed, indicating that a high-quality interface can be achieved using a Al₂O₃ IPL on an AlGaN substrate. Good surface passivation effects of the Al₂O₃ IPL have also been confirmed by pulsed gate measurements. Devices with 1- mum gate lengths exhibit a cutoff frequency (fT) of 12 GHz and a maximum frequency of oscillation (f _MAX) of 34 GHz, as well as a maximum drain current of 800 mA/mm and a peak transconductance of 150 mS/mm, whereas the gate leakage current is at least six orders of magnitude lower than that of the reference high-electron mobility transistors at a positive gate bias.