An ultra-low dark current CMOS image sensor cell using n/sup +/ ring reset

We present in this letter for the first time a new CMOS image sensor cell using n/sup +/-ring-reset structure, which can isolate the photon-sensing area from the defective field oxide edge. The experimental results demonstrate that the severe dark current degradation of the conventional CMOS active pixel image sensor fabricated by a standard CMOS logic process is significantly alleviated. Through optimizing the layout arrangement, as high as 45% fill factor can be obtained. The dynamic range of this new cell can thus be improved by more than 10/spl times/ compared to a conventional cell.     

Nitride-based LEDs with n/sup -/-GaN current spreading layers

Nitride-based light-emitting diodes (LEDs) with n/sup -/-GaN current spreading layers were proposed and fabricated. With a 0.1-/spl mu/m-thick n/sup -/-GaN current spreading layer, it was found that the output power could be enhanced by 35% without increasing the operation voltage of the LEDs at 20 mA. In addition, implementing the n/sup -/-GaN current spreading layer also significantly improved the electrostatic discharge characteristics of nitride-based LEDs.     

Characteristics of SOI CMOS circuits made in n/n+/n oxidised porous silicon structures

Porous silicon was formed in the highly doped layer of the n/n+/n structure. After full oxidation of porous silicon, CMOS devices were fabricated in insulated single-crystal silicon islands. Mobilities of 540 cm2/Vs and 180 cm2/Vs are found for N-channel and P-channel transistors with low spread of threshold voltages. Results also indicate very low leakage currents, typically less than 10?13 A/?m width. Processed wafers, 100 mm in diameter, are flat without evidence of any warpage.     

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.     

Er/sup 3+/ glass waveguide amplifier at 1.5 mu m on silicon

Highly Er/sup 3+/-doped sodium calcium silicate glass waveguide was fabricated on oxidised silicon wafers. An Er/sup 3+/ absorption of 8.5 dB/cm was measured at 1.53 mu m, whereas transmission loss outside the Er/sup 3+/ absorption band was estimated to be approximately 1 dB/cm. By pumping the waveguide with 120 mW of power at 975 nm the 1.53 mu m signal intensity was enhanced by 21 dB.<>     

High brightness InGaN green LEDs with an ITO on n/sup ++/-SPS upper contact

Indium tin oxide (ITO) (260 nm) and Ni (5 nm)/Au (10 nm) films were deposited onto glass substrates, p-GaN layers, n/sup +/-InGaN/GaN short-period-superlattice (SPS), n/sup ++/-SPS and nitride-based green light-emitting diodes (LEDs). It was found that ITO could provide us an extremely high transparency (i.e., 95% at 520 nm). It was also found that the 1.03/spl times/10/sup -3/ /spl Omega/cm/sup 2/ specific contact resistance of ITO on n/sup ++/-SPS was reasonably small. Although the forward voltage of the LED with ITO on n/sup ++/-SPS upper contacts was slightly higher than that of the LED with Ni/Au on n/sup ++/-SPS upper contacts, the 20 mA output power and external quantum efficiency of the former could reach 4.98 mW and 8.2%, respectively, which were much larger than the values observed from the latter. The reliability of ITO on n/sup ++/-SPS upper contacts was also found to be reasonably good.     

Modeling and optimization of short Er/sup 3+/-Yb/sup 3+/ codoped fiber lasers

A theoretical study of short Er/sup 3+/- Yb/sup 3+/ codoped fiber lasers (EYDFLs) is presented. Examples include centimeter-length EYDFLs pumped at 978 nm, with distributed Bragg reflector (DBR) mirrors at both fiber ends. Approximate quasi-analytical solutions are shown to be in excellent agreement with the exact numerical solution of the rate equations. Using the quasi-analytical model, we demonstrate a design optimization of a short EYDFL. The effects of the Yb/sup 3+/ concentration, laser wavelength, output mirror reflectivity, and pump wavelength are considered and discussed with relation to the optimal laser length and output efficiency.     

1.5-V single work-function W/WN/n/sup +/-poly gate CMOS device design with 110-nm buried-channel PMOS for 90-nm vertical-cell DRAM

This letter reports on 1.5-V single work-function W/WN/n/sup +/-poly gate CMOS transistors for high-performance stand-alone dynamic random access memory (DRAM) and low-cost low-leakage embedded DRAM applications. At V/sub dd/ Of 1.5-V and 25/spl deg/C, drive currents of 634 /spl mu/A//spl mu/m for 90-nm L/sub gate/ NMOS and 208 /spl mu/A-/spl mu/m for 110-nm L/sub gate/ buried-channel PMOS are achieved at 25 pA//spl mu/m off-state leakage. Device performance of this single work function technology is comparable to published low leakage 1.5-V dual work-function technologies and 25% better than previously reported 1.8-V single work-function technology. Data illustrating hot-carrier immunity of these devices under high electric fields is also presented. Scalability of single work-function CMOS device design for the 90-nm DRAM generation is demonstrated.     

Modeling and experiments of actively Q-switched Er/sup 3+/-Yb/sup 3+/ codoped clad-pumped fiber lasers

Two models are presented to describe the complex dynamics of Q-switched clad-pumped Er/sup 3+/-Yb/sup 3+/ codoped fiber lasers (EYDFLs): the full model that includes the full wavelength-dependence of parameters in the 1550- and the 1080-nm band due to Er/sup 3+/ and Yb/sup 3+/, respectively, and the simplified model that assumes single wavelengths for both bands. The models are based on detailed rate equations that include energy transfer between Er/sup 3+/ and Yb/sup 3+/ ions, and spontaneous emission due to both Er/sup 3+/ and Yb/sup 3+/. The simplified model is shown to agree with the full model within 10% difference. Experiments are performed using a 4-m-long single-mode clad-pumped EYDFL, and pulse energy of 14.5 /spl mu/J is achieved. Excellent agreement is shown between the simplified model and experiments. The model is further used to study the extractable energy of the laser and show limiting factors: amplified spontaneous emission (ASE) and energy storage in Yb/sup 3+/ ions. The model is also used to optimize the pulse energy in terms of fiber length, pump power, and Er/sup 3+/-Yb/sup 3+/ concentrations.     

Theoretical analysis of gain characteristics of Er/sup 3+/-Tm/sup 3+/-codoped tellurite fiber amplifier

The rate and power propagation equations of Er/sup 3+/ and Tm/sup 3+/-codoped tellurite fiber amplifier pumped by 800-nm laser are presented and solved to analyze the dependences of gain at both 1470 and 1530 nm on the codoping concentration of Er/sup 3+/ and Tm/sup 3+/, fiber length, and input signal power. The numerical results show that with pump power of 200 mW and fiber length of 1.5 m, the gain at both 1470 and 1530 nm may reach 12.0 dB when the codoping concentration of Er/sup 3+/ and Tm/sup 3+/ reach 4.0/spl times/10/sup 25/ ions/m/sup 3/, 3.2/spl times/10/sup 25/ ions/m/sup 3/, respectively. The fiber length and codopant concentrations are proposed to make the two channels equivalently amplified.     

Fabrication and photoluminescence characteristics of ER/sup 3+/-doped optical fibre sensitised by silicon

Er³⁺-doped optical fibres co-doped with silicon particles were fabricated by the modified chemical vapour deposition and the solution doping technique. Peak intensity of the photoluminescence at 1560 nm upon pumping by a CW Ar-ion laser at 512 nm was enhanced by about 70% after the silicon incorporation     

Single-pole double-throw CMOS switches for 900-MHz and 2.4-GHz applications on p/sup -/silicon substrates

A 900-MHz single-pole double-throw (SPDT) switch with an insertion loss of 0.5 dB and a 2.4-GHz SPDT switch with an insertion loss of 0.8 dB were implemented using 3.3-V 0.35-/spl mu/m NMOS transistors in a 0.18-/spl mu/m bulk CMOS process utilizing 20-/spl Omega//spl middot/cm p/sup -/ substrates. Impedance transformation was used to reduce the source and load impedances seen by the switch to increase the power handling capability. SPDT switches with 30-/spl Omega/ impedance transformation networks exhibit 0.97-dB insertion loss and 24.3-dBm output P/sub 1dB/ when tuned for 900-MHz operation, and 1.10-dB insertion loss and 20.6-dBm output P/sub 1dB/ when tuned for 2.4-GHz operation. The 2.4-GHz switch is the first bulk CMOS switch which can be used for 802.11b wireless local area network applications.     

Improved gain performance of high concentration Er/sup 3+/-Yb/sup 3+/-codoped phosphate fiber amplifier

The rate equations and power evolution equations of erbium/ytterbium codoped phosphate fiber amplifiers are solved numerically and its results are compared with measured data in literature. Based on the numerical analysis, optimal erbium and ytterbium codoping concentrations are supposed, and with a pump power of 224 mW and a fiber length of 3.6 cm, the internal gain of 31.0 dB and gain per unit length of 8.6 dB/cm may be achieved in the fiber with the optimal codoping concentrations.     

Gain characteristics of Pr/sup 3+/-Yb/sup 3+/ codoped fluoride fiber for 1.3 mu m amplification

The authors report on the ability of the Pr/sup 3+/-Yb/sup 3+/ codoped system to move the pumping wavelength to wavelengths shorter than 1.017 mu m. It was demonstrated that, by codoping of Yb/sup 3+/ with Pr/sup 3+/-doped fluoride fiber, amplifiers can be moved to the spectral range where effective pumping can be done with InGaAs laser diodes that have strained-layer quantum-well structures that were developed as a pumping source for Er/sup 3+/-doped fiber amplifiers. The pumping wavelength range was extended down to 0.93 mu m.<>     

W-band monolithic frequency doubler using vertical GaAs varactor diode with n/sup +/ buried layer

A W-band monolithic frequency doubler was designed and fabricated using a vertical GaAs varactor diode that has an n/sup +/ buried layer and uses a mesa isolation process. An output power of 30 mW was obtained from this chip at 93 GHz with a conversation efficiency of 12%. This is believed to be the first reported W-band monolithic varactor diode frequency doubler.<>     

A unique dual-poly gate technology for 1.2-V mobile DRAM with simple in situ n/sup +/-doped polysilicon

Highly manufacturable sub-100-nm 1.2-V mobile dynamic random access memory (DRAM) having full functionality and excellent reliability have been successfully developed. A unique and simple DRAM technology with dual-gate CMOSFET was realized using plasma-nitrided thin gate oxide and p/sup +/ poly gate formed by BF/sub 2/ ion implanted compensation of in situ phosphorus (n/sup +/) doped amorphous silicon gate. Using this technology, boron penetration into the channel, gate poly depletion, and dopant interdiffusion between n/sup +/- and p/sup +/-doped WSi/sub x/-polycide gates were successfully suppressed. In addition, a negatively biased word line scheme and a storage capacitor with laminated high-/spl kappa/ Al/sub 2/O/sub 3/ and HfO/sub 2/ dielectrics were also developed to achieve mobile DRAM operating at 1.2 V with excellent performance and reliability.     

Numerical analysis of optical amplification in Er/sup 3+/-Yb/sup 3+/ codoped Ti:LiNbO/sub 3/ strip waveguides

Optical amplification at 1530 nm in 980-nm pumped Er/sup 3+/-Yb/sup 3+/-diffused Ti:LiNbO/sub 3/ strip waveguides was numerically analyzed on the basis of rate equation model of Er/sup 3+/-Yb/sup 3+/ system and pump/signal power propagation equations. The model includes total eight energy levels of the Er/sup 3+/-Yb/sup 3+/ system and simultaneously takes into account the excited state absorption (ESA) and upconversion processes within the Er/sup 3+/ ions as well as possible energy transfer processes between Yb/sup 3+/ and Er/sup 3+/ ions. A comparison of numerical results from the eight-level model and highly simplified five-level model has indicated that the /sup 4/S/sub 3/2/ manifold of Er /sup 3+/ ion must be included in the rate equation model. Dependences of threshold pump power and amplification gain on pump power (for gain only), Yb/sup 3+/ surface concentration and waveguide length were calculated and discussed. The characteristics of pump power evolution along the waveguide axis and population density distribution, as well as the influences of energy transfer coefficient from Yb/sup 3+/ to Er/sup 3+/, 550-nm (Er/sup 3+/), and 1060-nm (Yb/sup 3+/) fluorescence lifetime and above-mentioned detrimental processes including ESA, upconversion, and cross-relaxation processes on numerical result were studied. The role of Yb/sup 3+/ is demonstrated. A novel design idea that Yb/sup 3+/ is only incorporated at the end of the waveguide is proposed.     

DC isolation and RF dissipation loss of coplanar waveguide on GaAs multi conductive Layers bombarded by H/sup +/ and Fe/sup +/ ions

This letter explores the dc isolation and radio frequency (RF) dissipation loss of coplanar waveguide (CPW) lines of H/sup +/ and Fe/sup +/ ion bombarded GaAs multi conductive epitaxial layers. It is demonstrated that although a sheet resistivity as high as 10/sup 8/ /spl Omega/sq has been achieved by ion bombardment, showing excellent dc isolation, the RF dissipation loss of gold metallized CPW lines on the bombarded multi conductive epitaxial layers are higher than that on a semi-insulating GaAs substrate, especially at higher frequencies (0.5 dB/cm higher at 50 GHz). This is probably caused by deep level trappings due to the ion bombardment.