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.<>     

Improved NiSi salicide process using presilicide N/sub 2//sup +/ implant for MOSFETs

An improved Ni salicide process has been developed by incorporating nitrogen (N/sub 2//sup +/) implant prior to Ni deposition to widen the salicide processing temperature window. Salicided poly-Si gate and active regions of different linewidths show improved thermal stability with low sheet resistance up to a salicidation temperature of 700 and 750/spl deg/C, respectively. Nitrogen was found to be confined within the NiSi layer and reduced agglomeration of the silicide. Phase transformation to the undesirable high resistivity NiSi/sub 2/ phase was delayed, likely due to a change in the interfacial energy. The electrical results of N/sub 2//sup +/ implanted Ni-salicided PMOSFETs show higher drive current and lower junction leakage as compared to devices with no N/sub 2//sup +/ implant.     

Fabrication and characterization of an InAs/sub 0.96/Sb/sub 0.04/ photodetector for MIR applications

In this letter, we report an InAsSb p/sup +/-n junction photodetector grown on InAs substrate by liquid phase epitaxy. Electrical and optical characterizations of the device have been carried out at room temperature for operation of the device in the mid-infrared region. The study revealed that the dark current of the photodetector under reverse bias is dominated by a trap-assisted tunnelling current component, which degrades the detectivity of the device. Further, by operating the device at a suitable low reverse bias it is possible to improve the room-temperature detectivity significantly as compared to its value at zero bias.     

High-responsivity high-gain In/sub 0.53/Ga/sub 0.47/As-InP quantum-well infrared photodetectors grown using metal-organic vapor phase epitaxy

We report the growth and fabrication of bound-to-bound In/sub 0.53/Ga/sub 0.47/As-InP quantum-well infrared photodetectors using metal-organic vapor phase epitaxy. These detectors have a peak detection wavelength of 8.5 /spl mu/m. The peak responsivities are extremely large with R/sub pk/=6.9 A/W at bias voltage V/sub b/=3.4 V and temperature T=10 K. These large responsivities arise from large detector gain that was found to be g/sub n/=82 at V/sub b/=3.8 V from dark current noise measurements at T=77 K and g/sub p/=18.4 at V/sub b/=3.4 V from photoresponse data at T=10 K. The background-limited temperature with F/1.2 optics is T/sub BLIP/=65 K for 0相似文献   

(Al/sub 0.5/Ga/sub 0.5/)/sub 0.65/In/sub 0.35/P/Ga/sub 0.65/In/sub 0.35/P double-heterostructure orange light-emitting diodes

Visible light-emitting diodes (LEDs) emitting at 615 nm and employing the AlGaInP/GaInP double heterostructure (DH) grown on a lattice-matched GaAs/sub 0.7/P/sub 0.3/ substrate have been fabricated for the first. The external quantum efficiency of 0.156% for the orange LEDs can be achieved by introducing the GaP material as the current spreader and window layer for the DH LEDs.<>     

InGaAs-InP mesa DHBTs with simultaneously high f/sub /spl tau// and f/sub max/ and low C/sub cb//I/sub c/ ratio

We report an InP-InGaAs-InP double heterojunction bipolar transistor (DHBT), fabricated using a conventional triple mesa structure, exhibiting a 370-GHz f/sub /spl tau// and 459-GHz f/sub max/, which is to our knowledge the highest f/sub /spl tau// reported for a mesa InP DHBT-as well as the highest simultaneous f/sub /spl tau// and f/sub max/ for any mesa HBT. The collector semiconductor was undercut to reduce the base-collector capacitance, producing a C/sub cb//I/sub c/ ratio of 0.28 ps/V at V/sub cb/=0.5 V. The V/sub BR,CEO/ is 5.6 V and the devices fail thermally only at >18 mW//spl mu/m/sup 2/, allowing dc bias from J/sub e/=4.8 mA//spl mu/m/sup 2/ at V/sub ce/=3.9 V to J/sub e/=12.5 mA//spl mu/m/sup 2/ at V/sub ce/=1.5 V. The device employs a 30 nm carbon-doped InGaAs base with graded base doping, and an InGaAs-InAlAs superlattice grade in the base-collector junction that contributes to a total depleted collector thickness of 150 nm.     

n/sup +/-InAs-InAlAs recess gate technology for InAs-channel millimeter-wave HFETs

We report a submicrometer, self-aligned recess gate technology for millimeter-wave InAs-channel heterostructure field effect transistors. The recess gate structure is obtained in an n/sup +/-InAs-InAlAs double cap layer structure with a citric-acid-based etchant. From molecular-beam epitaxy-grown material functional devices with 1000-, 500-, and 200-nm gate length were fabricated. From all three device geometries we obtain drive currents of at least 500 mA/mm, gate leakage currents below 2 mA/mm, and RF-transconductance of 1 S/mm. For the 200-nm gate length device f/sub /spl tau// and f/sub max/ are 162 and 137 GHz, respectively. For the 500-nm gate length device f/sub /spl tau// and f/sub max/ are 89 and 140 GHz, respectively. We observe scaling limitations at 200-nm gate length, in particular a negative threshold voltage shift from -550 to -810 mV, increased kink-effect, and a high gate-to-drain capacitance of 0.5 pF/mm. The present limitations to device scaling are discussed.     

Efficient amplification using the /sup 4/F/sub 3/2//spl rarr//sup 4/I/sub 9/2/ transition in Nd-doped silica fiber

Amplification characteristics of the three-level /sup 4/F/sub 3/2//spl rarr//sup 4/I/sub 9/2/ transition in Nd-doped silica glass fiber are investigated under strong signal saturation and high pump power (150 mW). Aluminum codoped Nd-silica fibers exhibit strong superfluorescent behavior in the four-level /sup 4/F/sub 3/2//spl rarr//sup 4/I/sub 11/2/ transition which limits the optical conversion efficiency into the three-level transition. Ge-doped silica fibers do not exhibit this limitation and can efficiently amplify in the three-level transition with current laser-diode pump technology.     

A resonant tunneling quantum-dot infrared photodetector

A novel device-resonant tunneling quantum-dot infrared photodetector-has been investigated theoretically and experimentally. In this device, the transport of dark current and photocurrent are separated by the incorporation of a double barrier resonant tunnel heterostructure with each quantum-dot layer of the device. The devices with In/sub 0.4/Ga/sub 0.6/As-GaAs quantum dots are grown by molecular beam epitaxy. We have characterized devices designed for /spl sim/6 /spl mu/m response, and the devices also exhibit a strong photoresponse peak at /spl sim/17 /spl mu/m at 300 K due to transitions from the dot excited states. The dark currents in the tunnel devices are almost two orders of magnitude smaller than those in conventional devices. Measured values of J/sub dark/ are 1.6/spl times/10/sup -8/ A/cm/sup 2/ at 80 K and 1.55 A/cm/sup 2/ at 300 K for 1-V applied bias. Measured values of peak responsivity and specific detectivity D/sup */ are 0.063 A/W and 2.4/spl times/10/sup 10/ cm/spl middot/Hz/sup 1/2//W, respectively, under a bias of 2 V, at 80 K for the 6-/spl mu/m response. For the 17-/spl mu/m response, the measured values of peak responsivity and detectivity at 300 K are 0.032 A/W and 8.6/spl times/10/sup 6/ cm/spl middot/Hz/sup 1/2//W under 1 V bias.     

Room-temperature InAsSb photovoltaic detectors for mid-infrared applications

Novel noncryogenic InAsSb photovoltaic detectors grown by molecular beam epitaxy are proposed and demonstrated. The quaternary alloy In/sub 0.88/Al/sub 0.12/As/sub 0.80/Sb/sub 0.20/ is introduced as a wide bandgap barrier layer lattice matched to the GaSb substrate. The valence band edge of In/sub 0.88/Al/sub 0.12/As/sub 0.80/Sb/sub 0.20/ nearly matches with InAs/sub 0.91/Sb/sub 0.09/, leading to more efficient transport of photogenerated holes. The resulting mid-infrared photovoltaic detector exhibits a 50% cutoff wavelength of 4.31 /spl mu/m and a peak responsivity of 0.84 A/W at room temperature. High Johnson-noise-limited detectivity (D/sup */) of 2.6/spl times/10/sup 9/ cm/spl middot/Hz/sup 1/2//W at 4.0 /spl mu/m, and 4.2/spl times/10/sup 10/ cm/spl middot/Hz/sup 1/2//W at 3.7 /spl mu/m are achieved at 300 K and 230 K, respectively.     

Characteristics of In/sub x/Al/sub 1-x/N-GaN high-electron mobility field-effect transistor

GaN-based field effect transistors commonly include an Al/sub x/Ga/sub 1-x/N barrier layer for confinement of a two-dimensional electron gas (2DEG) in the barrier/GaN interface. Some of the limitations of the Al/sub x/Ga/sub 1-x/N-GaN heterostructure can be, in principle, avoided by the use of In/sub x/Al/sub 1-x/N as an alternative barrier, which adds flexibility to the engineering of the polarization-induced charges by using tensile or compressive strain through varying the value of x. Here, the implementation and electrical characterization of an In/sub x/Al/sub 1-x/-GaN high electron mobility transistor with Indium content ranging from x=0.04 to x=0.15 is described. The measured 2DEG carrier concentration in the In/sub 0.04/Al/sub 0.96/N-GaN heterostructure reach 4/spl times/10/sup 13/ cm/sup -2/ at room temperature, and Hall mobility is 480 and 750 cm/sup 2//V /spl middot/ s at 300 and 10 K, respectively. The increase of Indium content in the barrier results in a shift of the transistor threshold voltage and of the peak transconductance toward positive gate values, as well as a decrease in the drain current. This is consistent with the reduction in polarization difference between GaN and In/sub x/Al/sub 1-x/N. Devices with a gate length of 0.7 /spl mu/m exhibit f/sub t/ and f/sub max/ values of 13 and 11 GHz, respectively.     

In/sub 0.5/Ga/sub 0.5/As/GaAs quantum dot infrared photodetectors grown by metal-organic chemical vapor deposition

We report the growth by low-pressure metal-organic chemical vapor deposition, fabrication, and characterization of ten-layer In/sub 0.5/Ga/sub 0.5/As/GaAs quantum dot infrared photodetectors. Normal incidence photoresponse of the detector was obtained at 5.9 /spl mu/m. The 77-K peak responsivity was 5.6 mA/W with the detectivity D/sup */ of 1.2/spl times/10/sup 9/ cm/spl middot/Hz/sup 1/2//W at the bias of 0.4 V.     

GaInAsSb/GaSb pn photodiodes for detection to 2.4 mu m

Ga/sub 0.77/In/sub 0.23/As/sub 0.20/Sb/sub 0.80//GaSb pn heterojunction photodiodes have been prepared by liquid phase epitaxy. They exhibit a long-wavelength threshold of 2.4 mu m. The room-temperature dark current at V=-0.5 V is 3 mu A (10 mA/cm/sup 2/) and the external quantum efficiency is around 40% in the wavelength range 1.75-2.25 mu m. The estimated detectivity D* at 2.2 mu m is 8.8*10/sup 9/ cm Hz/sup 1/2/ W/sup -1/.<>     

Cyclic codes over GR(4/sup m/) which are also cyclic over /spl Zopf//sub 4/

Let GR(4/sup m/) be the Galois ring of characteristic 4 and cardinality 4/sup m/, and /spl alpha/_={/spl alpha//sub 0/,/spl alpha//sub 1/,...,/spl alpha//sub m-1/} be a basis of GR(4/sup m/) over /spl Zopf//sub 4/ when we regard GR(4/sup m/) as a free /spl Zopf//sub 4/-module of rank m. Define the map d/sub /spl alpha/_/ from GR(4/sup m/)[z]/(z/sup n/-1) into /spl Zopf//sub 4/[z]/(z/sup mn/-1) by d/spl alpha/_(a(z))=/spl Sigma//sub i=0//sup m-1//spl Sigma//sub j=0//sup n-1/a/sub ij/z/sup mj+i/ where a(z)=/spl Sigma//sub j=0//sup n-1/a/sub j/z/sup j/ and a/sub j/=/spl Sigma//sub i=0//sup m-1/a/sub ij//spl alpha//sub i/, a/sub ij//spl isin//spl Zopf//sub 4/. Then, for any linear code C of length n over GR(4/sup m/), its image d/sub /spl alpha/_/(C) is a /spl Zopf//sub 4/-linear code of length mn. In this article, for n and m being odd integers, it is determined all pairs (/spl alpha/_,C) such that d/sub /spl alpha/_/(C) is /spl Zopf//sub 4/-cyclic, where /spl alpha/_ is a basis of GR(4/sup m/) over /spl Zopf//sub 4/, and C is a cyclic code of length n over GR(4/sup m/).     

A high-density MIM capacitor (13 fF//spl mu/m/sup 2/) using ALD HfO/sub 2/ dielectrics

Metal-insulator-metal (MIM) capacitors with different HfO/sub 2/ thickness have been investigated. The results show that both the capacitance density and voltage coefficients of capacitance (VCCs) increase with decreasing HfO/sub 2/ thickness. In addition, it is found that the VCCs decrease logarithmically with increasing thickness. Furthermore, the MIM capacitor with 10-nm HfO/sub 2/ shows a record high capacitance density of 13 fF//spl mu/m/sup 2/ and a VCC of 607 ppm/V, which can meet the requirement of the International Technology Roadmap for Semiconductors. It can also provide a low leakage current of 5.95 /spl times/ 10/sup -8/A/cm/sup 2/ at room temperature at 1 V, low tangent values below 0.05, and a small frequency dependence. These results indicate that the devices are suitable for use in silicon integrated circuit applications.     

Low-temperature MBE-grown In/sub 0.52/Ga/sub 0.18/Al/sub 0.30/As/InP optical waveguides

The MBE growth of In/sub 0.52/Ga/sub 0.18/Al/sub 0.30/As ( lambda /sub g/=1.06 mu m) layers in the temperature range of 400-450 degrees C was demonstrated to give high-quality optical waveguides which not only exhibit low propagation losses as low as 0.5 dB/cm at lambda =1.55 mu m but concomitantly high resistivity of >10/sup 4/ Omega cm. The refractive index of In/sub 0.52/Ga/sub 0.18/Al/sub 0.30/As was estimated to be 3.207+or-0.03 at lambda =1.55 mu m.<>     

1330 V, 67 m/spl Omega//spl middot/cm/sup 2/ 4H-SiC(0001) RESURF MOSFET

Design and fabrication of 4H-SiC(0001) lateral MOSFETs with a two-zone reduced surface field structure have been investigated. The dose dependencies of experimental breakdown voltage show good agreement with simulation. Through the optimization of implant dose, high-temperature (1700/spl deg/C) annealing after ion implantation, and reduction of channel length, a breakdown voltage of 1330 V and a low on-resistance of 67 m/spl Omega//spl middot/cm/sup 2/ have been obtained. The figure-of-merit (V/sub B//sup 2//R/sub on/) of the present device reaches 26 MW/cm/sup 2/, being the best performance among lateral MOSFETs reported. The temperature dependence of static characteristics is also presented.     

A novel high-/spl kappa/ SONOS memory using TaN/Al/sub 2/O/sub 3//Ta/sub 2/O/sub 5//HfO/sub 2//Si structure for fast speed and long retention operation

A novel high-/spl kappa/ silicon-oxide-nitride-oxide-silicon (SONOS)-type memory using TaN/Al/sub 2/O/sub 3//Ta/sub 2/O/sub 5//HfO/sub 2//Si (MATHS) structure is reported for the first time. Such MATHS devices can keep the advantages of our previously reported TaN/HfO/sub 2//Ta/sub 2/O/sub 5//HfO/sub 2//Si device structure to obtain a better tradeoff between long retention and fast programming as compared to traditional SONOS devices. While at the same time by replacing hafnium oxide (HfO/sub 2/) with aluminum oxide (Al/sub 2/O/sub 3/) for the top blocking layer, better blocking efficiency can be achieved due to Al/sub 2/O/sub 3/'s much larger barrier height, resulting in greatly improved memory window and faster programming. The fabricated devices exhibit a fast program and erase speed, excellent ten-year retention and superior endurance up to 10/sup 5/ stress cycles at a tunnel oxide of only 9.5 /spl Aring/ equivalent oxide thickness.     

Path to the measurement of positive gain on the 1315-nm transition of atomic iodine pumped by O/sub 2/(a/sup 1//spl Delta/) produced in an electric discharge

Laser action at 1315 nm on the I(/sup 2/P/sub 1/2/)/spl rarr/I(/sup 2/P/sub 3/2/) transition of atomic iodine is conventionally obtained by a near-resonant energy transfer from O/sub 2/(a/sup 1//spl Delta/) which is produced using wet-solution chemistry. The system difficulties of chemically producing O/sub 2/(a/sup 1//spl Delta/) have motivated investigations into gas phase methods to produce O/sub 2/(a/sup 1//spl Delta/) using low-pressure electric discharges. We report on the path that led to the measurement of positive gain on the 1315-nm transition of atomic iodine where the O/sub 2/(a/sup 1//spl Delta/) was produced in a flowing electric discharge. Atomic oxygen was found to play both positive and deleterious roles in this system, and as such the excess atomic oxygen was scavenged by NO/sub 2/ to minimize the deleterious effects. The discharge production of O/sub 2/(a/sup 1//spl Delta/) was enhanced by the addition of a small proportion of NO to lower the ionization threshold of the gas mixture. The electric discharge was upstream of a continuously flowing supersonic cavity, which was employed to lower the temperature of the flow and shift the equilibrium of atomic iodine more in favor of the I(/sup 2/P/sub 1/2/) state. A tunable diode laser system capable of scanning the entire line shape of the (3,4) hyperfine transition of iodine provided the gain measurements.     

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.