Characteristics of HfO/sub 2/ pMOSFET prepared by B/sub 2/H/sub 6/ plasma doping and KrF excimer laser annealing

The electrical characteristics of HfO/sub 2/ pMOSFETs prepared by B/sub 2/H/sub 6/ plasma doping and excimer laser annealing were investigated. Various metal gate electrodes were evaluated to protect the high-/spl kappa/ oxide during laser irradiation. Although the aluminum gate electrode showed superior reflectivity to the laser, the equivalent oxide thickness was increased due to the interaction between aluminum and HfO/sub 2/, which resulted in reduced capacitance. In contrast, the Al-TaN stacked gate showed good reflectivity up to laser energy of 500 mJ/cm/sup 2/ and improved capacitance was obtained compared with the Al gate. For the first time, the electrical characteristics of a HfO/sub 2/ pMOSFET with an Al-TaN gate fabricated by plasma doping and excimer laser annealing were demonstrated. It was also demonstrated that plasma doping and excimer laser annealing combined with a metal gate could be applied for high-/spl kappa/ oxide MOSFET fabrication.     

Preparation and growth of thin film Pb/sub 2/Sr/sub 2/Ca/sub 0.5/Y/sub 0.5/Cu/sub 3/O/sub 8+ delta / superconductors by laser ablation

For the first time, the preparation of thin films of superconducting Pb/sub 2/Sr/sub 2/Y/sub 0.5/Ca/sub 0.5/Cu/sub 3/O/sub 8+ delta / material using standard bulk target preparation conditions and the laser ablation technique is reported. In common with much of the bulk characteristics, it is found that the width of the superconducting transition is large, extending from T/sub c,onset/ between 70-83 K and T/sub c,zero/ between 16-20 K.<>     

Operating characteristics of CW CO/sub 2/-N/sub 2/O laser

The authors have obtained the emission characteristics of a CW CO/sub 2/-N/sub 2/O laser. The CO/sub 2/ laser lines and N/sub 2/O laser lines vary according to the applied condition. Thus the operating conditions are interpreted.<>     

Modelocked Cr/sup 3+/:LiSr/sub 0.8/Ca/sub 0.2/AlF/sub 6/ laser producing 150 fs pulses

Mode-locked operation has been achieved in a CW pumped Cr/sup 3+/:LiSr/sub 0.8/Ca/sub 0.2/AlF/sub 6/ laser. Pulses of 150 fs duration were directly generated from the actively mode-locked laser. A CW krypton laser operating with 1 W in the red was used to pump the 15 mm long crystal.<>     

CHD/sub 2/OH optically pumped by a waveguide CO/sub 2/ laser: new far-infrared laser lines from the CD/sub 2/ wagging vibrational mode

For the first time, a wide tunability waveguide CO/sub 2/ laser was used to pump the CHD/sub 2/OH molecule for the generation of new FIR laser lines with a large offset. Optoacoustic signals associated with the infrared absorbing transitions of the CD/sub 2/ wagging vibrational mode served as a guide for finding new laser lines. All lines were characterized in wavelength, relative polarization, intensity, optimum pressure of operation, and precise offset measurements.     

Laser operation of epitaxially grown Yb:KLu(WO/sub 4/)/sub 2/--KLu(WO/sub 4/)/sub 2/ composites with monoclinic Crystalline structure

Epitaxial monoclinic double tungstate composites based on the strongly anisotropic KLu(WO/sub 4/)/sub 2/ (KLuW) were grown with high crystalline quality and laser operation of ytterbium was demonstrated for the first time. Highly efficient CW laser emission of an Yb:KLuW-KLuW crystal was achieved near 1030 nm. The 100-/spl mu/m-thick Yb:KLuW layer was pumped at wavelengths near 980 nm by a tapered diode laser as well as by a Ti:sapphire laser. More than 500 mW of CW output power and slope efficiencies up to 66% were obtained at room temperature without cooling.     

Spectroscopic analysis and diode-pumped laser results of Nd:BaY/sub 2/F/sub 8/

Single crystals of monoclinic BaY/sub 2/F/sub 8/, doped with different Nd/sup 3+/ concentrations, were successfully grown by means of the Czochralski method. Here, we present a polarized infrared (IR) spectroscopic investigation and diode-pumped continuous-wave laser results in the 1 /spl mu/m wavelength region. Moreover for the first time 1.3 /spl mu/m laser emission has been characterized. Q-switching results in the 1-/spl mu/m region are also presented.     

Modeling of continuous-wave self-frequency-doubling microchip laser for Yb/sup 3+/:YAl/sub 3/(BO/sub 3/)/sub 4/ crystal

Based on a quasi-three-level system, a model of continuous wave (CW) self-frequency-doubling (SFD) laser for the end-pumped Yb/sup 3+/:YAl/sub 3/(BO/sub 3/)/sub 4/ (Yb/sup 3+/:YAB) microchip is proposed. The effect of fluorescence concentration quenching (FCQ), the temperature distribution in the microchip medium, and then the refractive index distribution resulting from the thermal effect in the medium, the absorption of host, and the spatial distribution of SFD beam have been taken into account in the model. The calculated results are compared with those of experiments, and it reveals that this model is reasonable. It can be applied not only to the CW SFD laser of the Yb/sup 3+/:YAB microchip, but also to the quasi-three-level CW SFD laser of other microchips.     

Ga/sub 0.8/In/sub 0.2/As/GaAs/Ga/sub 0.51/In/sub 0.49/P buried ridge structure single quantum well laser emitting at 0.98 mu m

The first fabrication is reported of a buried ridge structure Ga/sub 0.8/In/sub 0.2/As/GaAs/Ga/sub 0.51/In/sub 0.49/P laser emitting at 0.98 mu m grown by two-step low pressure metal organic chemical vapour deposition. The width of the ridge is 2 mu m. Laser output power greater than 40 mW with a threshold current of 30 mA has been measured. A typical quantum efficiency of eta =60% was obtained without any facet coating. Excellent homogeneity and uniformity have been achieved over a wafer area of 10 cm/sup 2/.<>     

Optical pumping of CHD/sub 2/OH and CH/sub 2/DOH methanol isotopomers by means of a new pulsed CO/sub 2/ laser: characterization of new far-infrared laser emissions

We have reinvestigated CHD/sub 2/OH and CH/sub 2/DOH methanol isotopomers as sources of far-infrared laser radiation using the optical pumping technique. A new waveguide pulsed CO/sub 2/ laser was used, that delivers high peak powers also in the 10-HP CO/sub 2/ band and has allowed us to observe 19 new far-infrared emissions from CHD/sub 2/OH and 8 new far-infrared emissions from CH/sub 2/DOH. Each of them is characterized in wavelength, pump offset from the center of the exciting CO/sub 2/ line, relative polarization, optimum operating pressure and intensity.     

Lasing at three-dimensionally quantum-confined sublevel of self-organized In/sub 0.5/Ga/sub 0.5/As quantum dots by current injection

A laser oscillation from self-organized In/sub 0.5/Ga/sub 0.5/As quantum dots is achieved at 80 K by current injection. Lasing at a three-dimensionally quantum confined sublevel of the In/sub 0.5/Ga/sub 0.5/As quantum dots is clearly demonstrated for the first time by electroluminescence and diamagnetic energy shift measurement. The results predict the possibility of ultra-low threshold current operation of quantum dot lasers.     

Erbium spectroscopy and 1.5-/spl mu/m emission in KGd(WO/sub 4/)/sub 2/: Er,Yb single crystals

We grew good-optical-quality KGd(WO/sub 4/)/sub 2/ single crystals doped with erbium and ytterbium ions at several concentrations of dopants using the top-seeded-solution growth slow-cooling method (TSSG). We performed the spectroscopic characterization of this material related to the 1.5-mm infrared emission of erbium which is interesting for laser applications. To do this, we carried out polarized optical absorption at room temperature (RT) and at low temperature (6 K) and performed luminescence studies of the emission and lifetime. We obtained the 1.5-mm emission of erbium after selective laser pump excitation of the ytterbium ion and energy transfer between the two ions. The maximum emission cross section for 1.5 mm was about 2.56/spl times/10/sup -20/ cm/sup 2/ for the polarization of light with the electric field parallel to the N/sub m/ principal optical direction. This value was higher than for other erbium-doped materials with application in solid-state lasers such as LiYF/sub 4/:Er(YLF:Er), Y/sub 3/Al/sub 5/O/sub 12/:Er(YAG:Er), YAlO/sub 3/:Er, and Al/sub 2/O/sub 3/:Er.     

Vertical integration of an In/sub 0.15/Ga/sub 0.85/As modulation-doped field effect transistor and GaAs laser grown by molecular beam epitaxy

A vertically integrated structure consisting of an In/sub 0.15/Ga/sub 0.85/As pseudomorphic modulation doped field effect transistor (MODFET) and a GaAs graded index separate confinement heterostructure single quantum well (GRINSCH SQW) laser was grown by molecular beam epitaxy. Wafers containing integrated MODFET/laser layers produced MODFETs with DC and microwave performance comparable to wafers containing only MODFET layers, indicating that the modulation doping and the strained In/sub 0.15/Ga/sub 0.85/As channel were largely unaffected by the long, high temperature laser growth. The lasers had threshold currents similar to identical structures grown on n-type substrates and the integrated structures had a -3dB modulation bandwidth of 3.5 GHz.<>     

A novel strained Si/sub 0.7/Ge/sub 0.3/ surface-channel pMOSFET with an ALD TiN/Al/sub 2/O/sub 3//HfAlO/sub x//Al/sub 2/O/sub 3/ gate stack

Proof-of-concept pMOSFETs with a strained-Si/sub 0.7/Ge/sub 0.3/ surface-channel deposited by selective epitaxy and a TiN/Al/sub 2/O/sub 3//HfAlO/sub x//Al/sub 2/O/sub 3/ gate stack grown by atomic layer chemical vapor deposition (ALD) techniques were fabricated. The Si/sub 0.7/Ge/sub 0.3/ pMOSFETs exhibited more than 30% higher current drive and peak transconductance than reference Si pMOSFETs with the same gate stack. The effective mobility for the Si reference coincided with the universal hole mobility curve for Si. The presence of a relatively low density of interface states, determined as 3.3 /spl times/ 10/sup 11/ cm/sup -2/ eV/sup -1/, yielded a subthreshold slope of 75 mV/dec. for the Si reference. For the Si/sub 0.7/Ge/sub 0.3/ pMOSFETs, these values were 1.6 /spl times/ 10/sup 12/ cm/sup -2/ eV/sup -1/ and 110 mV/dec., respectively.     

Blue energy upconversion emission in thulium-doped-SiO/sub 2/-P/sub 2/O/sub 5/ channel waveguides excited at 1.064 /spl mu/m

Blue energy upconversion emission in Tm/sup 3+/-doped SiO/sub 2/-P/sub 2/O/sub 5/ channel waveguides off-resonance pumped by infrared radiation is reported. The waveguide samples were excited by a single continuous-wave laser source at 1.064 /spl mu/m. Two distinct blue emission signals around 450 and 480 nm, in addition to red at 660 nm and near-infrared at 800-nm less intense emissions were observed. The upconversion excitation mechanism was assigned to stepwise multiphoton absorption processes followed by nonradiative multiphonon-assisted relaxation processes. Infrared-to-blue conversion efficiencies with respect to the absorbed pump power of /spl sim/6.0/spl times/10/sup -7/ for this off-resonance pumping scheme was measured. The dependence of the infrared-to-blue upconversion mechanism upon the excitation power and thulium content is also examined.     

MIM capacitors using atomic-layer-deposited high-/spl kappa/ (HfO/sub 2/)/sub 1-x/(Al/sub 2/O/sub 3/)/sub x/ dielectrics

Metal-insulator-metal (MIM) capacitors with (HfO/sub 2/)/sub 1-x/(Al/sub 2/O/sub 3/)/sub x/ high-/spl kappa/ dielectric films were investigated for the first time. The results show that both the capacitance density and voltage/temperature coefficients of capacitance (VCC/TCC) values decrease with increasing Al/sub 2/O/sub 3/ mole fraction. It was demonstrated that the (HfO/sub 2/)/sub 1-x/(Al/sub 2/O/sub 3/)/sub x/ MIM capacitor with an Al/sub 2/O/sub 3/ mole fraction of 0.14 is optimized. It provides a high capacitance density (3.5 fF//spl mu/m/sup 2/) and low VCC values (/spl sim/140 ppm/V/sup 2/) at the same time. In addition, small frequency dependence, low loss tangent, and low leakage current are obtained. Also, no electrical degradation was observed for (HfO/sub 2/)/sub 1-x/(Al/sub 2/O/sub 3/)/sub x/ MIM capacitors after N/sub 2/ annealing at 400/spl deg/C. These results show that the (HfO/sub 2/)/sub 0.86/(Al/sub 2/O/sub 3/)/sub 0.14/ MIM capacitor is very suitable for capacitor applications within the thermal budget of the back end of line process.     

Spectroscopic and stimulated emission characteristics of Nd/sup 3+/ in transparent Y/sub 2/O/sub 3/ ceramics

Nd:Y/sub 2/O/sub 3/ ceramic materials have been synthesized using the vacuum sintering technique with the raw materials prepared by the nanocrystalline methods. The TEM measurements reveal the excellent optical quality of the ceramic with low pore volume and narrow grain boundary. The radiative spectral properties of Nd:Y/sub 2/O/sub 3/ ceramic have been evaluated by fitting the Judd-Ofelt model with the absorption and emission data. Individual Stark levels for /sup 2s+1/L/sub J/ manifolds are obtained from the absorption and fluorescence spectra and are analyzed to identify the stimulated emission channels possible in the Nd:Y/sub 2/O/sub 3/ ceramic. Laser performance studies reveal two stimulated emission channels at 1074.6- and 1078.6-nm wavelengths with stimulated emission cross sections of 7.63/spl times/10/sup -20/ and 6.35/spl times/10/sup -20/ cm/sup 2/. With 1.5 at % Nd:Y/sub 2/O/sub 3/ ceramic acting as a laser medium, we obtained a slope efficiency of 32% with 160-mW output power and pump threshold of 200 mW at 1078.6 nm.     

Modeling of tunneling currents through HfO/sub 2/ and (HfO/sub 2/)/sub x/(Al/sub 2/O/sub 3/)/sub 1-x/ gate stacks

We present a physical modeling of tunneling currents through ultrathin high-/spl kappa/ gate stacks, which includes an ultrathin interface layer, both electron and hole quantization in the substrate and gate electrode, and energy band offsets between high-/spl kappa/ dielectrics and Si determined from high-resolution XPS. Excellent agreements between simulated and experimentally measured tunneling currents have been obtained for chemical vapor deposited and physical vapor deposited HfO/sub 2/ with and without NH/sub 3/-based interface layers, and ALD Al/sub 2/O/sub 3/ gate stacks with different EOT and bias polarities. This model is applied to more thermally stable (HfO/sub 2/)/sub x/(Al/sub 2/O/sub 3/)/sub 1-x/ gate stacks in order to project their scalability for future CMOS applications.     

Refractive index step and optical confinement in Ga/sub 0.86/In/sub 0.14/As/sub 0.13/Sb/sub 0.87//Ga/sub 0.73/Al/sub 0.27/As/sub 0.02/Sb/sub 0.98/ double heterostructure lasers emitting at 2.2 mu m

Using theoretical fitting to measured transverse far field patterns in Ga/sub 0.86/In/sub 0.14/As/sub 0.13/Sb/sub 0.87//Ga/sub 0.73/Al/sub 0.27/As/sub 0.02/Sb/sub 0.98/ DH lasers emitting at 2.2 mu m the authors estimated the value of the active layer refractive index as 3.78. This value, higher than assumed earlier based on theoretical calculations, ensures good optical confinement for this kind of heterostructure and provides a good theoretical fit with the authors' experimental data of threshold current density against active layer thickness.<>     

CO/sub 2/ laser processing of alumina (Al/sub 2/O/sub 3/) printed circuit board substrates

We report the results of an investigation of the laser-material interaction processes involved in laser drilling of alumina, through the use of an enhanced peak power (2.5 kW) CO/sub 2/ laser and novel temporal pulse formats. Peak power was varied from 30 W to 2 kW for pulses of constant energy to observe the effect produced on scribe depth. High-speed videography of hole formation has been combined with microscopic analysis to investigate the key processes involved in laser processing of alumina. Plasma screening was observed for short, high peak power laser pulses, and optimal scribing was achieved in the weakly plasma absorbing regime. A new processing technique for scribing alumina has been developed, which exploits the fast response of the laser to produce novel temporal pulse shapes, which can be modified to generate cleaner holes. Scribe speeds of up to 280 mm/spl middot/s/sup -1/ were obtained for scribe holes >200 /spl mu/m deep and 150 /spl mu/m apart, with no material plugging the hole, in 0.635-mm-thick 96% alumina.