DEVELOPMENT OF CURRENT-BASED MICROSCOPIC DEFECT ANALYSIS-METHODS AND ASSOCIATED OPTICAL FILLING TECHNIQUES FOR THE INVESTIGATION ON HIGHLY IRRADIATED HIGH-RESISTIVITY SILICON DETECTORS

Current based microscopic defect analysis methods such as current deep level transient spectroscopy (I-DLTS) and thermally stimulated current (TSC) have been further developed in accordance with the need for the defect analysis of highly irradiated (Phi(n) > 10(13) n/cm(2)) high resistivity silicon detectors. The new I-DLTS/TSC system has a temperature range of 8 K less than or equal to T less than or equal to 450 K and a high sensitivity that can detect a defect concentration of less than 10(10)/cm(3) (background noise as low as 10 fA). A new filling method using different wavelength laser illumination has been applied, which is more efficient and suitable than the traditional voltage pulse filling. It has been found that the filling of a defect level depends on such factors as the total concentration of free carriers generated or injected, the penetration length of the laser (laser wavelength), the temperature at which the filling is taking place, as well as the decay time after the filling (but before the measurement). The mechanism of the defect filling can be explained by the competition between trapping and detrapping of defect levels, possible capture cross section temperature dependence, and interaction among various defect levels in terms of charge transferring. Optimum defect filling conditions have been suggested for highly irradiated high resistivity silicon detectors.

A voltage-controlled ring oscillator using InP full enhancement-mode HEMT logic

A voltage-controlled ring oscillator (VCO) based on a full enhancement-mode InAIAs/InGaAs/InP high electron mobility transistor (HEMT) logic is proposed. An enhancement-mode HEMT (E-HEMT) is fabricated, whose threshold is demonstrated to be 10 mV. The model of the E-HEMT is established and used in the SPICE simulation of the VCO. The result proves that the full E-HEMT logic technology can be applied to the VCO. And compared with the HEMT DCFL technology, the complexity of our fabrication process is reduced and the reliability is improved.

A high speed direct digital frequency synthesizer realized by a segmented nonlinear DAC

This paper presents a high speed ROM-less direct digital frequency synthesizer (DDFS) which has a phase resolution of 32 bits and a magnitude resolution of 10 bits. A 10-bit nonlinear segmented DAC is used in place of the ROM look-up table for phase-to-sine amplitude conversion and the linear DAC in a conventional DDFS.The design procedure for implementing the nonlinear DAC is presented. To ensure high speed, current mode logic (CML) is used. The chip is implemented in Chartered 0.35μm COMS technology with active area of 2.0 × 2.5 mm~2 and total power consumption of 400 mW at a single 3.3 V supply voltage. The maximum operating frequency is 850 MHz at room temperature and 1.0 GHz at 0 ℃.

Fabrication of an AlAs/In0.53Ga0.47As/InAs Resonant Tunneling Diode on InP Substrate for High-Speed Circuit Applications

A high performance AlAs/In0.53 Ga0.47 As/InAs resonant tunneling diode （RTD） on InP substrate is fabricated by inductively coupled plasma etching. This RTD has a peak-to-valley current ratio （PVCR） of 7. 57 and a peak current density Jp = 39.08kA/cm^2 under forward bias at room temperature. Under reverse bias, the corresponding values are 7.93 and 34.56kA/cm^2 . A resistive cutoff frequency of 18.75GHz is obtained with the effect of a parasitic probe pad and wire. The slightly asymmetrical current-voltage characteristics with a nominally symmetrical structure are also discussed.

A Wide-Band High-Linearity Down-Conversion Mixer for Cable Receptions

We analyze a wide-band,high-linearity down-conversion mixer for cable receptions that is implemented in 0. 35μm SiGe BiCMOS technology. The bandwidth of the RF （radio frequency） input covers the range from 1 to 1.8GHz. The measured input power at the - 1dB compression point of the mixer reaches ＋ 14.23dBm. The highest voltage conversion gain is 8. 31dB, while the lowest noise figure is 19.4dB. The power consumed is 54mW with a 5V supply. The test result of the down-conversion mixer is outlined.

High Temperature Characteristics of 3C-SiC/Si Heterojunction Diodes Grown by LPCVD

The high temperature (300～480K) characteristics of the n-3C-SiC/p-Si heterojunction diodes (HJD) fabricated by low-pressure chemical vapor deposition on Si (100) substrates are investigated.The obtained diode with best rectifying properties has 1.8×104 of ratio at room temperature,and slightly rectifying characteristics with 3.1 of rectification ratio is measured at 480K of an ambient temperature .220V of reverse breakdown voltage is acquired at 300K.Capacitance-voltage characteristics show that the abrupt junction model is applicable to the SiC/Si HJD structure and the built-in voltage is 0.75V.An ingenious equation is employed to perfectly simulate and explain the forward current density-voltage data measured at various temperatures.The 3C-SiC/Si HJD represents a promising approach for the fabrication of high quality heterojunction devices such as SiC-emitter heterojunction bipolar transistors.

A novel high sensitivity CE-PTHPT for optical fiber communication

Planar punch through heterojunction phototransistors with a novel emitter control electrode and ion- implanted isolation (CE-PTHPT) are investigated. The phototransistors have a working voltage of 3-10V and high sensitivity at low input power. The base of the transistor is completely depleted under operating condition. Base current is zero. The CE-PTHPT has an increased speed and a decreased noise. The novel CE-PTHPT has been fabricated in this paper. The optical gain of GaAlAs/GaAs CE-PTHPT for the incident light power 1.3 and 43nw with the wavelength of 0.8 mu m reached 1260 and 8108. The input noise current calculated is 5.46 x 10(-16) A/H-z(1/2). For polysilicon emitter CE-PTHPT, the optical gain is 3083 at the input power of 0.174 mu w. The optical gain of InGaAs/InP CE-PTHPT reaches 350 for an incident power of 0.3 mu w at the wavelength of 1.55 mu m. The CE-PTHPT detectors is promising as photo detectors for optical fiber communication system.

Study on shunt impedance and voltage distribution of 4-rod RFQ cavity

A high current RFQ (radio frequency quadrupole) is being studied at the Institute of Modern Physics, CAS for the direct plasma injection scheme. Shunt impedance is air important parameter when designing a 4-rod RFQ cavity, it reflects the RF efficiency of the cavity, and has a direct influence on the cost of the structure. Voltage distribution of a RFQ cavity has an effect on beam transmission, and particles would be lost if the actual voltage distribution is not as what, it should be. The influence of cell length, stern thickness and height on Shunt impedance and voltage distribution have been studied, in particular the effect of projecting electrodes has been investigated in detail.

Performance improvement in direct methanol fuel cell cathode using high mesoporous area catalyst support

Black Pearls 2000 (designated as BP- 2000) and Vulcan XC-72 (designated as XC-72) carbon blacks were chosen as supports to prepare 40 wt % (the targeted value) Pt/C catalysts by a modified polyol process. The carbon blacks were characterized by N-2 adsorption and Fourier tranform infrared spectroscopy. The prepared catalysts were characterized by inductively coupled plasma atomic emission spectroscopy, transmission electron microscopy, scanning electron microscopy (SEM), in situ cyclic voltammetry, and current-voltage curves. On BP- 2000, Pt nanoparticles were larger in size and more unevenly distributed than on XC-72. It was observed by SEM that the corresponding catalyst layer on BP- 2000 was thicker than that of XC-72 based catalyst at almost the identical catalyst loading. And the BP- 2000 supported catalyst gave a better single cell performance at high current densities. These results suggest that the performance improvement is due to the enhanced oxygen diffusion and water removal capability when BP- 2000 is used as cathode catalyst support. (C) 2004 The Electrochemical Society.

An Efficient Nanocrystalline La2O3:Tm3+ Blue Phosphor for Field-Emission Displays with High Color Purity

Nanocrystalline Tm3+-doped La2O3 phosphors were prepared through a Pechini-type sol-gel process. X-ray diffraction, field-emission scanning electron microscopy, photoluminescence, and cathodoluminescence spectra were utilized to characterize the synthesized phosphors. Under the excitation of UV light (234 nm) and low-voltage electron beams (1-3 kV), the Tm3+-doped La2O3 phosphors show the characteristic emissions of Tm3+(D-1(2), (1)G(4)-F-3(4), H-3(6) transitions).

Large current gain and low operational voltage permeable metal-base organic transistors based on Au/Al double layer metal base

In order to realize the common-emitter characteristics of the tris(8-hydroxyquinoline) aluminium (Alq(3))-based organic transistors, we used Au/Al double metal layer as the base, thus the vertical metal-base transistors with structure of Al/n-Si/Au/Al/Alq(3)/LiF/Al were constructed. It was found that the contact properties between the base and the organic semiconductors play an important role in the device performance. The utilization of Au/Al double layer metal base allows the devices to operate at high gain in the common-emitter and common-base mode at low operational voltage.

Hybrid permeable metal-base transistor with large common-emitter current gain and low operational voltage

We demonstrate the suitability of N,N'-diphenyl-N,N'-bis(1-naphthylphenyl)-1,1'-biphenyl-4,4'-diamine (NPB), an organic semiconductor widely used in organic light-emitting diodes (OLEDs), for high-gain, low operational voltage nanostructured vertical-architecture transistors, which operate as permeable-base transistors. By introducing vanadium oxide (V2O5) between the injecting metal and NPB layer at the transistor emitter, we reduced the emitter operational voltage.

Tungsten oxide doped N,N-'-di(naphthalen-1-yl)-N,N-'-diphenyl-benzidine as hole injection layer for high performance organic light-emitting diodes

By introducing tungsten oxide (WO3) doped N,N-'-di(naphthalen-1-yl)-N,N-'-diphenyl-benzidine (NPB) hole injection layer, the great improvement in device efficiency and the organic film morphology stability at high temperature were realized for organic light-emitting diodes (OLEDs). The detailed investigations on the improvement mechanism by optical, electric, and film morphology properties were presented. The experimental results clearly demonstrated that using WO3 doped NPB as the hole injection layer in OLEDs not only reduced the hole injection barrier and enhanced the transport property, leading to low operational voltage and high efficiency, but also improved organic film morphology stability, which should be related to the device stability. It could be seen that due to the utilization of WO3 doped NPB hole injection layer in NPB/tris (8-quinolinolato) aluminum (Alq(3))-based device, the maximum efficiency reached 6.1 cd A(-1) and 4.8 lm W-1, which were much higher than 4.5 cd A(-1) and 1.1 lm W-1 of NPB/Alq(3) device without hole injection layer. The device with WO3 doped NPB hole injection layer yet gave high efficiency of 6.1 cd A(-1) (2.9 lm W-1) even though the device was fabricated at substrate temperature of 80 degrees C.

Lead(IV) dioxide: an effective electron injection material to realize high-efficiency inverted top-emitting organic light-emitting diodes

Lead(IV) dioxide (PbO2) has been used as the electron injection layer (EIL) to realize high-efficiency inverted top-emitting organic light-emitting diodes (I-TOLEDs). It can be seen that the inserting of the PbO2 EIL significantly reduces operational voltage, thus greatly improving the current efficiency and power efficiency of fabricated I-TOLEDs. The 10-(2-benzothiazolyl)-1, 1, 7, 7-tetramethyl-2, 3, 6, 7-tetrahydro-1H, 5H, 11H-[1] benzopyrano [6, 7, 8-ij] quinolizin-11-one (C545T)-based I-TOLEDs with the PbO2 EIL exhibit a maximum current efficiency of 31.6 cd A(-1) and a maximum power efficiency of 14.3 lm W-1, which are both higher than 22.5 cd A(-1) and 5.4 lm W-1 of the I-TOLEDs with LiF as the EIL respectively. A detailed analysis with respect to the role mechanism of PbO2 in electron injection has been presented. The improvement in EL performance is attributed to the formation of the interfacial dipoles at the electrode interface due to charge transfer between PbO2 and Alq(3).

Nanocrystalline LaGaO3 : Tm3+ as an efficient blue phosphor for field emission displays with high color purity

Nanocrystalline Tm3+-doped LaGaO3 phosphors were prepared through a Pechini-type sol-gel process [M. P. Pechini, U.S. Patent No. 3,330,697 (11 July 1967)]. X-ray diffraction, field emission scanning electron microscopy, photoluminescence, and cathodoluminescence (CL) spectra were utilized to characterize the synthesized phosphors. Under the excitation of ultraviolet light and low voltage electron beams (0.5-3 kV), the Tm3+-doped LaGaO3 phosphors show the characteristic emissions from the LaGaO3 host lattice and the Tm3+ (D-1(2), (1)G(4)-F-3(4), and H-3(6) transitions), respectively. The blue CL of the Tm3+-doped LaGaO3 phosphors, with a dominant wavelength of 458 nm, had better Commission International I'Eclairage chromaticity coordinates (0.1552, 0.0630) and higher emission intensity than the commercial product (Y2SiO5:Ce3+).