Zn$_{1 - x}$Mg$_{x}$ O Homojunction-Based Ultraviolet Photodetector

Zn$_{1 - {x}}$ Mg$_{x}$ O p-n photodiodes were fabricated on (0001) sapphire substrates using a pulsed laser deposition technique with different Mg contents. Ti–Au and Ni–Au metals deposited using vacuum evaporation were used as n-type and p-type contacts, respectively. The X-ray diffraction analysis showed the Zn$_{1 - {x}}$Mg$_{x}$O double layers have a single phase hexagonal wurtzite structure. The optical bandgap of Zn$_{1 - {x}}$Mg$_{x}$O films has been tuned from 3.27 to 4.26 eV by increasing the Mg content ${x} =0.0$ to ${x}=0.34$. Correspondingly, the cutoff wavelength of the resultant detectors varies from 380 to 284 nm. Zn$_{1 - {x}}$Mg$_{x}$O p-n photodiodes with different Mg contents exhibit very good performance, with a very low dark current (${≪}$ 20 pA) at the bias voltage of 10 V. The ultraviolet to visible rejection ratio is more than three orders of magnitude.      

Nitride-Based Asymmetric Two-Step Light-Emitting Diode With In$_{0.08}$ Ga$_{0.92}$ N Shallow Step

A nitride-based asymmetric two-step light-emitting diode (LED) with $hbox{In}_{0.08} hbox{Ga}_{0.92}hbox{N}$ shallow step was proposed and fabricated. It was found that the low indium content $hbox{In}_{0.08} hbox{Ga}_{0.92}hbox{N}$ layer can significantly enhance phase separation and/or inhomogeneous indium distribution in the active $hbox{In}_{0.27}hbox{Ga}_{0.73}hbox{N}$ layer. It was also found that we can enhance LED output power by a factor of 2.27 by simply inserting an $hbox{In}_{0.08} hbox{Ga}_{0.92}hbox{N}$ shallow step.      

Enhanced Vertical Light Extraction From Ultrathin Amorphous Si–Si$_{3}$ N$_{4}$ Multilayers With Photonic Crystal Patterns

We have investigated the significant enhancement of light extraction from amorphous Si-Si₃N₄ multiple-quantum-well structures, in which two-dimensional hexagonal-lattice air-hole photonic crystals (PCs) were integrated. The vertical spectral integrated intensity of light emission around 674 nm was enhanced up to times due to strong coupling to the inherent leaky modes or radiation modes near Gamma point of PC's band structure. The experimental observations also suggested that coupling to leaky modes should be more beneficial for light extraction enhancement.     

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.     

Frequencies and Wavelengths From a New Far-Infrared Lasing Gas: $^{13}$ CHD$_{2}$ OH

The first laser action produced by the partially deuterated isotopic form of methanol, $^{13}$ CHD$_{2}$ OH, has been observed. With this laser medium, eight far-infrared laser emissions were discovered having wavelengths ranging from 33.8 to 80.9 $mu$m. A three-laser heterodyne system was used to measure the frequencies for these newly discovered laser lines and are reported with fractional uncertainties of ${pm}3 times 10^{-7}$. The offset frequency of the CO$_{2}$ pump laser was measured with respect to its center frequency for each $^{13}$CHD$_{2}$OH laser emission.      

Chalcogenide As$_{2}$S$_{3}$ Suspended Core Fiber for Mid-IR Wavelength Conversion Based on Degenerate Four-Wave Mixing

A chalcogenide optical fiber of special design is proposed to convert a short-wavelength infrared radiation (around 2 $mu$m) up to a second transparency window of atmospheric air (around 4.5 $mu$ m) by degenerate four-wave mixing. The fiber supports a small core surrounded by three large air holes. The zero-dispersion wavelength is shifted down to 2 $mu$m in this fiber by properly tailoring the fiber core. We demonstrate by solving the nonlinear SchrÖdinger equation that efficient wavelength-conversion can be obtained by pumping the fiber with a Tm : SiO$_{2}$ pulsed fiber laser.      

High Density and Low Leakage Current in $ hbox{TiO}_{2}$ MIM Capacitors Processed at 300 $^{circ} hbox{C}$

We report Ir/TiO₂/TaN metal-insulator-metal capacitors processed at only 300degC, which show a capacitance density of 28 fF/mum² and a leakage current of 3 times 10^-8 (25degC) or 6 times 10^-7 (125degC) A/cm² at -1 V. This performance is due to the combined effects of 300degC nanocrystallized high-kappa TiO₂, a high conduction band offset, and high work-function upper electrode. These devices show potential for integration in future very-large-scale-integration technologies.     

Reliable Low-Cost Fabrication of Low-Loss $hbox{Al}_{2}hbox{O} _{3}{:}hbox{Er}^{3+}$ Waveguides With 5.4-dB Optical Gain

A reliable and reproducible deposition process for the fabrication of Al₂O₃ waveguides with losses as low as 0.1 dB/cm has been developed. The thin films are grown at ~ 5 nm/min deposition rate and exhibit excellent thickness uniformity within 1% over 50times50 mm² area and no detectable OH^- incorporation. For applications of the Al₂O₃ films in compact, integrated optical devices, a high-quality channel waveguide fabrication process is utilized. Planar and channel propagation losses as low as 0.1 and 0.2 dB/cm, respectively, are demonstrated. For the development of active integrated optical functions, the implementation of rare-earth-ion doping is investigated by cosputtering of erbium during the Al₂O₃ layer growth. Dopant levels between 0.2-5times10²⁰ cm^-3 are studied. At Er³⁺ concentrations of interest for optical amplification, a lifetime of the ⁴I_13/2 level as long as 7 ms is measured. Gain measurements over 6.4-cm propagation length in a 700-nm-thick Al₂O₃:Er³⁺ channel waveguide result in net optical gain over a 41-nm-wide wavelength range between 1526-1567 nm with a maximum of 5.4 dB at 1533 nm.     

Achieving Low-$V_{T}$ Ni-FUSI CMOS by Ultra-Thin $hbox{Dy}_{2}hbox{O}_{3}$ Capping of Hafnium Silicate Dielectrics

This letter reports that the effective work function (eWF) of Ni-Fully Silicided (Ni-FUSI) devices with HfSiON gate dielectrics can be modulated toward the silicon conduction band-edge by deposition of an ultra-thin Dy₂O₃ cap layer on the host dielectric. The obtained eWF depends on the deposited cap layer thickness and the Ni-FUSI phase, with 10 Aring Dy₂O₃ cap resulting in DeltaeWF ap 400 meV and final eWF ap 4.08 eV for NiSi-FUSI. Dielectric intermixing occurs without impacting the VT uniformity, gate leakage, mobility, and reliability. Well-behaved short-channel devices ( Lg ~ 100 nm, SS ~ 70 mV/dec, and DIBL ~ 65 mV/V) are demonstrated for both HfSiON and [HfSiON/Dy₂O₃ cap (5 Aring)] devices with NiSi-FUSI gates, corresponding to a similar . This capping approach, when combined with Ni-silicide FUSI phase engineering, allows (n-p) values up to 800 meV, making it promising for low- CMOS.     

Compact Bends for Achieving Higher Integration Densities for LiNbO$_{3}$ Waveguides

A new waveguide platform is demonstrated that allows the bend radii to be substantially decreased for titanium-diffused lithium-niobate (LiNbO₃) waveguides using vertically integrated arsenic-trisulfide (As₂S₃) overlay waveguides. Power is transferred from a Ti-diffused waveguide into the overlay waveguide using tapers, guided by the As₂S₃ waveguide through the S-bend region and transferred back into another Ti-diffused waveguide. This structure also behaves like a polarization beam splitter. We present simulation results as well as measurements to show the feasibility of achieving low loss and reduced bend radii for electrooptic waveguides.     

Explosively Consolidated Powder-In-Tube MgB$_{2}$ Superconductor Aided by Post-Thermal Treatment

A MgB₂ superconductor was prepared from Mg flakes or powders and B powders using the powder-in-tube technique with explosive consolidation. Compaction of Mg and B powders resulted in a two-phase alloy, due to the relatively low temperature developed during compaction as well as the very short duration of the process. Formation of MgB₂ was obtained after subsequent heat treatment in argon atmosphere at a maximum temperature of 950degC.     

Performance Improvement of $hbox{Sm}_{2}hbox{O}_{3}$ MIM Capacitors by Using Plasma Treatment After Dielectric Formation

In this letter, we investigate the dependence of the performance of metal-insulator-metal (MIM) capacitors with Sm₂O₃ dielectric on plasma treatment (PT) performed before Sm₂O₃ deposition, after Sm₂O₃ deposition, or both before and after Sm₂O₃ deposition. By performing PT in N₂ ambient (PTN) after Sm₂O₃ dielectric formation, the effective quadratic voltage coefficient of capacitance (VCC) can be reduced from 498 to 234 ppm/V² and the effective linear VCC can be reduced from 742.3 to 172 ppm/V for MIM capacitor with Sm₂O₃ dielectric having a capacitance density of ~ 7.5 fF/mum². The leakage current density at +3.3 V can be reduced from 3.44 10^-7 to 1.60 times 10^-8 A/cm² by performing PTN in both before and after Sm₂O₃ deposition. PTN after dielectric formation is an effective way to improve the performance of high-kappa dielectric MIM capacitors for RF and analog/mixed signal IC applications.     

2 MHz AO $Q$ -switched ${rm TEM}_{00}$ Grazing Incidence Laser With 3 at.% Neodymium Doped Nd:YVO$_{4}$

We present a detailed experimental and theoretical study of the ultrahigh repetition rate AO $Q$ -switched ${rm TEM}_{00}$ grazing incidence laser. Up to 2.1 MHz $Q$-switching with ${rm TEM}_{00}$ output of 8.6 W and 2.2 MHz $Q$ -switching with multimode output of 10 W were achieved by using an acousto-optics $Q$ -switched grazing-incidence laser with optimum grazing-incidence angle and cavity configuration. The crystal was 3 at.% neodymium doped Nd:YVO$_{4}$ slab. The pulse duration at 2 MHz repetition rate was about 31 ns. The instabilities of pulse energy at 2 MHz repetition rate were less than ${pm}6.7hbox{%}$ with ${rm TEM}_{00}$ operation and ${pm}3.3hbox{%}$ with multimode operation respectively. The modeling of high repetition rate $Q$-switched operation is presented based on the rate equation, and with the solution of the modeling, higher pump power, smaller section area of laser mode, and larger stimulated emission cross section of the gain medium are beneficial to the $Q$-switched operation with ultrahigh repetition rate, which is in consistent with the experimental results.      

$hbox{In}_{0.53}hbox{Ga}_{0.47}hbox{As}$ Channel MOSFETs With Self-Aligned InAs Source/Drain Formed by MEE Regrowth

Abstract-We report Al₂O₃Zln_0.53Ga_0.47As MOSFETs having both self-aligned in situ Mo source/drain ohmic contacts and self-aligned InAs source/drain n⁺ regions formed by MBE regrowth. The device epitaxial dimensions are small, as is required for 22-nm gate length MOSFETs; a 5-nm In_0.53Ga_0.47As channel with an In_0.4sAl_0.52As back confinement layer and the n⁺⁺ source/drain junctions do not extend below the 5-nm channel. A device with 200-nm gate length showed I_D = 0.95 mA/mum current density at V_GS = 4.0 V and g_m = 0.45 mS/mum peak transconductance at V_DS = 2.0 V.     

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.      

A 67 dBm $OIP_{3}$ Multistacked Junction Varactor

A multistacked varactor is presented for ultra-linear tunable radio frequency applications. The varactor elements are applied in anti-series configuration and are characterized by an “exponential” $C$- $V _{R}$ relationship. Third-order intermodulation ($IM_{3}$) is cancelled through proper harmonic loading of the terminals of the anti-series configuration. Multiple stacking is used to further increase the power handling and to minimize the remaining fifth-order distortion. The measured output intercept point ($OIP_{3}$ ) at 2 GHz is $ > 67~{rm dBm}$ for modulated signals up to 10 MHz bandwidth, while providing a capacitance tuning ratio of 3:1 with an average quality factor of 40 and maximum control voltage of 10 V.      

Electrical Properties of Low-$V_{T}$ Metal-Gated n-MOSFETs Using $hbox{La}_{2}hbox{O}_{3}/hbox{SiO}_{x}$ as Interfacial Layer Between HfLaO High- $kappa$ Dielectrics and Si Channel

In this letter, we report that by employing the La₂O₃/SiO_x interfacial layer between HfLaO (La = 10%) high- and Si channel, the Ta₂C metal-gated n-MOSFETs V_T can be significantly reduced by ~350 mV to 0.2 V, satisfying the low-Vy device requirement. The resultant n-MOSFETs also exhibit an ultrathin equivalent oxide thickness (~1.18 nm) with a low gate leakage (J_G = 10 mA/cm² at 1.1 V), good drive performance (I_on = 900 muA/mum at I_soff = 70 nA/mum), and acceptable positive-bias-temperature-instability reliability.     

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.     

High-Reflectivity Thermally Stable Ultrafast Induced Fiber Bragg Gratings in H$_{2}$ -Loaded SMF-28 Fiber

High-temperature stable high-reflectivity gratings are fabricated in hydrogen-loaded single-mode fiber (SMF-28) using ultrafast 800-nm radiation. An index modulation of $sim 9times 10^{-4}$ and a loss of $>$15 dB at the Bragg resonance is present after isochronal annealing up to 1000 $^{circ}hbox{C}$ followed by 96 h of isothermal annealing.      

The Performance of Acoustic-Optical $Q$-switched Mode-Locking 1.34 $mu$m Nd:GdVO$_{4}$ Laser

A diode-end-pumped $Q$ -switched mode-locking $hbox{Nd:GdVO}_{4}$ laser operating at 1.34 $mu{hbox {m}}$ with an acousto-optical (AO) Q-switch in a compact V-type cavity was realized in our experiment for the first time. When the AO Q-switch repetition rate was 10 kHz, the maximum average output power of 750 mW and the pulse energy of 75 $muhbox{J}$ were obtained at the maximum incident pump power of 9 W. The mode-locking modulation depth of about 100% was obtained at certain pump power over the threshold. The mode-locked pulse inside in the $Q$-switched pulse had a repetition rate of 341 MHz, and its average pulsewidth was estimated to be about 350 ps. A developed rate equation model for the $Q$ -switched and mode-locked lasers with an AO Q-switch were proposed by using the hyperbolic secant functional methods. The results of numerical calculations of the rate equations were in good agreement with the experimental results.