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Volume 27, Issue 4, Apr 2006

  • Status and Trends in Advanced SOI Devices and Materials

    Balestra Francis

    Chin. J. Semicond.  2006, 27(4): 573

    Abstract PDF

    A review of recently explored effects in advanced SOI devices and materials is given.The effects of key device parameters on the electrical and thermal floating body effects are shown for various device architectures.Recent advances in the understanding of the sensitivity of electron and hole transport to the tensile or compressive uniaxial and biaxial strains in thin film SOI are presented.The performance and physical mechanisms are also addressed in multi-gate Si,SiGe and Ge MOSFETs.New hot carrier phenomena are discussed.The effects of gate misalignment or underlap,as well as the use of the back gate for charge storage in double-gate nanodevices and of capacitorless DRAM are also outlined.

  • REVIEWS

  • The Usage of Two Dielectric Function Models

    Chen Hong, Shen Wenzhong

    Chin. J. Semicond.  2006, 27(4): 583

    Abstract PDF

    This paper presents an overview of the history,modifications,characteristics,and applications of two well known dielectric function models--the Forouhi-Bloomer model and the Tauc-Lorentz model--which have been widely used for the extraction and parameterization of optical constants in semiconductors and dielectrics.Based on analysis of their inherent characteristics and comparison via demonstrative examples,deeper and wider usage of the two models is predicted.

  • PAPERS

  • Status and Trends in Advanced SOI Devices and Materials

    Wang Tianxing, Wei Hongxiang, Ren Cong, Han Xiufeng, Clifford E, Langford R M, Bari M A, Coey J M D

    Chin. J. Semicond.  2006, 27(4): 591

    Abstract PDF

    A new method of nanocontact fabrication for Adreev reflection measurement based on the nanopore method using a SiN membrane with focused ion beam technique is presented.With this method,controllable,clean,tensionless nano-contacts for spin polarization probing can be obtained.Measurements of the fabricated samples show complicated spectral structures with a zero bias anomaly and dip structures from quasipartical interactions.A control sample of Co40Fe40B20 is measured with Nb tip method.None of the measured spectra can be explained satisfactorily by present theory.Further analysis of the contact interface and a more complete theory are needed to extract a reliable spin polarization message with the point contact Andreev reflection method.

  • Transport Properties of Two Coupled Quantum Dots Under Optical Pumping

    Ge Chuannan, Wen Jun, Peng Ju, Wang Baigeng

    Chin. J. Semicond.  2006, 27(4): 598

    Abstract PDF

    Using the Keldysh-Green function,we present a theoretical study on the electron transport properties of two coupled quantum dots under optical pumping.Plateaus in the I-V curve and resonant peaks in the transmission coefficient occur and can be explained by the local electron density of states in the quantum dots.The effects of the optical pumping frequency and intensity on the transport properties of the system are also discussed.The electron dynamical localization phenomenon occurs when the optical pumping frequency is equal to the discrete hole energy level.This result can be used to realize optical control switches.

  • Effect of Relaxation Time on Electron Transport Properties in Double-Barrier Structures

    Dai Zhenhong, Ni Jun

    Chin. J. Semicond.  2006, 27(4): 604

    Abstract PDF

    Using a time-dependent quantum-kinetic simulation for the non-equilibrium electron transport properties of double-barrier devices,we have investigated and analyzed the effects of the relaxation time on electron transport properties in this kind of low dimensional structure.The results show that the relaxation time,which comes from the electron-phonon and electron-defect interactions,greatly affects the current-voltage curves,including the plateau-like gradient and hysteresis width of the current.

  • Nonlinear Current-Voltage Characteristics and Electroluminescence of cBN Crystal

    Dou Qingping, Chen Zhanguo, Jia Gang, Ma Haitao, Cao Kun, Zhang Tiechen

    Chin. J. Semicond.  2006, 27(4): 609

    Abstract PDF

    The current-voltage(I-V) characteristics of cBN crystal sandwiched between two metallic electrodes are measured and found to be nonlinear.Over 20 samples are measured at room temperature with various electrodes,and the resulting curves are all similar in shape.When a voltage of about 560V is applied to the cBN crystal,the emitted light is visible to the naked eye in a dark room.We explain these phenomena by the space charge limited current and the electronic transition between the X and Γ alleys of the conduction band.

  • Growth and Optical Properties of ZnO Films and Quantum Wells

    Zhang Baoping, Kang Junyong, Yu Jinzhong, Wang Qiming, Segawa Yusaburo

    Chin. J. Semicond.  2006, 27(4): 613

    Abstract PDF

    The growth characteristics during metalorganic chemical vapor deposition and optical properties of ZnO films on sapphire (Al2O3) (0001) and (1120) substrates are studied.For the former,the effects of two important growth parameters,i.e.temperature and pressure,are investigated in detail.Due to the large lattice mismatch between the film and the substrate,ZnO nanocrystals are usually obtained.The growth behavior at the film-substrate interface is found to be strongly dependent on the growth temperature,while the growth pressure determines the shape of the nanostructures as they grow.It is difficult to obtain ZnO films that have good quality and a smooth surface simultaneously.Due to the smaller lattice mismatch,the critical thickness of ZnO on the Al2O3 (1120) surface is found to be much larger than that on the Al2O3 (0001) surface.ZnO/MgZnO quantum wells with graded well thicknesses are grown on the Al2O3 (1120) surfaces,and their optical properties are studied.The built-in electric field in the well layer,generated by the piezoelectric effect,is estimated to be 3E5V/cm.It is found that growth at low temperatures and low pressures may facilitate the incorporation of acceptor impurities in ZnO.

  • Effect of Nickel Contamination on Formation of Denuded Zone in Czochralski Silicon

    Wu Dongdong, Yang Deren, Xi Zhenqiang, Que Duanlin, Zhong Yao

    Chin. J. Semicond.  2006, 27(4): 623

    Abstract PDF

    The effect of nickel contamination under rapid thermal processing (RTP) on the magic denuded zone (MDZ) in Czochralski silicon is investigated.It is found that the bulk defects can effectively getter nickel atoms once the MDZ forms.However,if the silicon sample is initially contaminated with nickel,the MDZ cannot form during the subsequent RTP,and a high density of precipitates occurs near the surface.In conventional IG processes,the DZ can form regardless of the nickel contamination sequence.Based on the facts,we propose that the formation of nickel silicide (Ni3Si) at the surface keeps the concentration of vacancies in the near-surface zone still higher than the critical concentration for oxygen precipitation under the subsequent RTP,which prevents MDZ formation.

  • Terahertz Semiconductor Quantum Well Devices

    Liu H C, Luo H, Ban D, Wachter M, Song C Y, Wasilewski Z R, Buchanan M, Aers G C, SpringThorpe A J, Cao J C, Feng S L, Williams B S, Hu Q

    Chin. J. Semicond.  2006, 27(4): 627

    Abstract PDF

    For eventually providing terahertz science with compact and convenient devices,terahertz (1~10THz) quantum-well photodetectors and quantum-cascade lasers are investigated.The design and projected detector performance are presented together with experimental results for several test devices,all working at photon energies below and around optical phonons.Background limited infrared performance (BLIP) operations are observed for all samples (three in total),designed for different wavelengths.BLIP temperatures of 17,13,and 12K are achieved for peak detection frequencies of 97THz(31μm),54THz(56μm),and 32THz(93μm),respectively.A set of THz quantum-cascade lasers with identical device parameters except for doping concentration is studied.The δ-doping density for each period varies from 3.2E10 to 4.8E10cm-2.We observe that the lasing threshold current density increases monotonically with doping concentration.Moreover,the measurements for devices with different cavity lengths provide evidence that the free carrier absorption causes the waveguide loss also to increase monotonically.Interestingly the observed maximum lasing temperature is best at a doping density of 3.6E10cm-2.

  • GaAsSb/InAlAs PA DHBTs Grown by Production MBE

    Zhu H J, Kuo J M, Pinsukanjana P, , Vargason K, Herrera M, Ontiveros D, Boehme C, Kao Y C

    Chin. J. Semicond.  2006, 27(4): 635

    Abstract PDF

    The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4×100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor.The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb.A Sb composition variation of less than ±0.1 atomic percent across a 4×100mm platen configuration has been achieved.The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO>6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm×50μm.The devices have a 40nm thick GaAsSb base with p-doping of 4.5E19cm-3.Devices with an emitter size of 4μm×30μm have a current gain variation less than 2% across the fully processed 100mm wafer.ft andfmax are over 50GHz,with a power efficiency of 50%,which are comparable to standard power GaAs HBT results.These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.

  • Monolithically Fabricated OEICs Using RTD and MSM

    Hu Yanlong, Liang Huilai, Li Yihuan, Zhang Shilin, Mao Luhong, Guo Weilian

    Chin. J. Semicond.  2006, 27(4): 641

    Abstract PDF

    Two kinds of monolithically fabricated circuits are demonstrated in GaAs-based material systems using resonant tunneling diodes(RTD) and metal-semiconductor-metal photo detectors(MSM PD).The electronic char-acteristics of these fabricated RTD devices,MSM devices,and integrated circuits are tested at room temperature.The results show that the current peak-to-valley ratio is 4,and the photocurrent at 5V is enhanced by a factor of nearly 9,from 2 to about 18μA by use of recessed electrodes.The working theory and logical functions of the circuits are validated.

  • A Novel Method to Compensate the Sigma-Delta Shaped Noise for Wide Band Fractional-N Frequency Synthesizers

    Shi Hao, Liu Junhua, Zhang Guoyan, Liao Huailin, Huang Ru, Wang Yuangyuan

    Chin. J. Semicond.  2006, 27(4): 646

    Abstract PDF

    A novel method to partially compensate sigma-delta shaped noise is proposed.By injecting the compensation current into the passive loop filter during the delay time of the phase frequency detector(PFD),a maximum reduction of the phase noise by about 16dB can be achieved.Compared to other compensation methods,the technique proposed here is relatively simple and easy to implement.Key building blocks for realizing the noise cancellation,including the delay variable PFD and compensation current source,are specially designed.Both the behavior level and circuit level simulation results are presented.

  • A DC-Offset Cancellation Scheme in a Direct-Conversion Receiver for IEEE 802.11a WLAN

    Xu Qiming, Shi Yin, Gao Peng, Hu Xueqing, Yan Jun, Xu Hua, Chen Hongda

    Chin. J. Semicond.  2006, 27(4): 653

    Abstract PDF

    A DC-offset cancellation scheme in a 5GHz direct-conversion receiver compliant with the IEEE 802.11a wireless LAN standard is presented.An analog feedback loop is used to eliminate the DC-offset at the output of the double-balanced mixer.The test results show that the mixer with the DC-offset cancellation circuit has a voltage conversion gain of 9.5dB at 5.15GHz,a noise figure of 13.5dB,an IIP3 of 7.6dBm,a DC-offset voltage of 1.73mV eliminating 76% of DC-offset,and a power consumption of 67mW with a 3.3V supply.The direct conversion WLAN receiver has been implemented in 0.35μm SiGe BiCMOS technology.

  • Design of a Silicon Beam Resonator for a Novel Gas Sensor

    Hao Yilong, Xu Jiajia, Zhang Guobing, Wu Guoying, Yan Guizhen

    Chin. J. Semicond.  2006, 27(4): 658

    Abstract PDF

    A new silicon beam resonator design for a novel gas sensor based on simultaneous conductivity and mass change measurement is investigated.High selectivity and sensitivity in gas detection can be obtained by measuring the charge-to-mass ratio of gas molecules.Structures of silicon beam resonators are designed,simulated,and optimized.This gas sensor is fabricated using sacrificial layer microelectronmechanical system technology,and the resonant frequency of the microbeam is measured.

  • MEMS Inductor Consisting of Suspended Thick Crystalline Silicon Spiral with Copper Surface Coating

    Wu Wengang, Li Yi, Huang Fengyi, Han Xiang, Zhang Shaoyong, Li Zhihong, Hao Yilong

    Chin. J. Semicond.  2006, 27(4): 662

    Abstract PDF

    A novel MEMS inductor consisting of a planar single crystalline silicon spiral with a copper surface coating as the conductor is presented.Using a silicon-glass anodic bonding and deep etching formation-and-release process,a 40μm-thick silicon spiral is formed,which is suspended on a glass substrate to eliminate substrate loss.The surfaces of the silicon spiral are coated with highly conformal copper by electroless plating to reduce the resistive loss in the conductor,with thin nickel film plated on the surface of the copper layer for final surface passivation.The fabricated inductor exhibits a self-resonance frequency higher than 15GHz,with a quality factor of about 40 and an inductance of over 5nH at 11.3GHz.Simulations based on a compact equivalent circuit model of the inductor and parameter extraction using a characteristic-function approach are carried out,and good agreement with measurements is obtained.

  • Parameter Extraction for 2-π Equivalent Circuit Modelof RF CMOS Spiral Inductors

    Gao Wei, Yu Zhiping

    Chin. J. Semicond.  2006, 27(4): 667

    Abstract PDF

    A novel parameter extraction method with rational functions is presented for the 2-π equivalent circuit model of RF CMOS spiral inductors.The final S-parameters simulated by the circuit model closely match experimental data.The extraction strategy is straightforward and can be easily implemented as a CAD tool to model spiral inductors.The resulting circuit models will be very useful for RF circuit designers.

  • Energy Transfer Probability Between Host and Guest in Doped Organic Electrophosphorescent Devices

    Li Hongjian, Ouyang Jun, Dai Guozhang, Dai Xiaoyu, Pan Yanzhi, Xie Qiang

    Chin. J. Semicond.  2006, 27(4): 674

    Abstract PDF

    An expression for energy transfer probability (η) between host (TPD) and guest (Ir(ppy)3) phosphorescent systems is proposed,and the energy transfer process in doped organic electrophosphorescent (EP) devices is discussed.The results show that (1) The rate of the triplet energy transfer (KHG and KGH) exponentially increases with the host-guest molecular distance (R),and KHG decreases quickly as the intermolecular distance of the guest (RGG) increases.In addition,the KHG/KGH ratio of the dopant system increases when R or RGG is reduced;(2) The energy transfer probability approximately linearly decreases as R increases from 0.8 to 12nm,and the variation of RGG can be neglected when R<1.1nm.For 1.1nm<R<1.2nm,RGG(<1.6nm) plays an increasingly important role when η drops with the latter;(3) η increases when the Forster energy transfer rate increases or Gibb’s energy declines.

  • Single Mode Operation of Short-Cavity Quantum Cascade Lasers

    Liu Fengqi, Guo Yu, Li Lu, Shao Ye, Liu Junqi, Lu Xiuzhen, Wang Zhanguo

    Chin. J. Semicond.  2006, 27(4): 679

    Abstract PDF

    Single mode operation of strain-compensated In1-xGaxAs/In1-yAlyAs quantum cascade lasers emitting at λ≈5.4 and 8μm is realized by shortening the Fabry-Perot cavity length.Accurate control of growth parameters and strain balance results in a perfect lattice match and thus in excellent material quality.Single mode emission with a side mode suppression ratio greater than 20dB for uncoated lasers is realized.Record low threshold currents of 50 and 80mA and record short cavity lengths of 145 and 170μm are achieved for λ≈5.4μm and λ≈7.84μm devices,respectively,in pulsed mode.

  • Optimization Design of Superluminescent Diodes with RWGStructure for High Efficiency Coupling with SMFs

    Zhong Xin, Huang Yidong, Zhao Han, Zhang Wei, Peng Jiangde

    Chin. J. Semicond.  2006, 27(4): 683

    Abstract PDF

    With the aim of achieving high coupling power of RWG SLDs into SMFs,the structure dependences of the output power and the near field pattern are investigated.The thicknesses of the layers between the active region and the ridge waveguide are optimized by taking into account the injected carrier distribution and local material gain in the SLD cross section.

  • An Open-Loop Test of a Resonator Fiber Optic Gyro

    Zhang Xulin, Ma Huilian, Jin Zhonghe, Ding Chun

    Chin. J. Semicond.  2006, 27(4): 688

    Abstract PDF

    The resonator fiber optic gyro (R-FOG),which utilizes a resonance frequency change due to the Sagnac effect,is a promising candidate for the next generation inertial rotation sensor.In this study,an open-loop R-FOG is set up using phase modulation spectroscopy.First,the demodulation curve is obtained using a lock-in amplifier.From the demodulation signal,a gyro dynamic range of ±4.2rad/s is obtained.Then,using different phase modulation frequencies,the open-loop gyro output signal is measured when the gyro is rotated clockwise or counterclockwise.The bias drift as a function of time is also measured.The fluctuation of the output over 5s is about 0.02rad/s.The drift can be reduced by taking countermeasures against system noise.

  • A 1×4 Polymeric Digital Optical Switch Basedon the Thermo-Optic Effect

    Tang Yi, Zhang Hao, Yang Jianyi, Wang Minghua, Jiang Xiaoqing

    Chin. J. Semicond.  2006, 27(4): 692

    Abstract PDF

    We present a 1×4 Y-branch digital optical switch in which S-bend variable optical attenuators are integrated.The S-bend waveguides,which are always introduced to connect the switch and the standard fiber array,are made use of and designed as variable optical attenuators.A compact device with low crosstalk and larger branching-angle is obtained.The device is fabricated on the thermo-optic polymer materials,and the performance of the device is measured.With an applied driving power of less than 200mW,the device has a low crosstalk of less than -35dB at a wavelength of 155μm

  • 30Gbit/s Parallel Optical Receiver Module

    Chen Hongda, Jia Jiuchun, Pei Weihua, Tang Jun

    Chin. J. Semicond.  2006, 27(4): 696

    Abstract PDF

    A 30Gbit/s receptor module is developed with a CMOS integrated receiver chip(IC) and a GaAs-based 1×12 photo detector array of PIN-type.Parallel technology is adopted in this module to realize a high-speed receiver module with medium speed devices.A high-speed printed circuit board(PCB) is designed and produced.The IC chip and the PD array are packaged on the PCB by chip-on-board technology.Flip chip alignment is used for the PD array accurately assembled on the module so that a plug-type optical port is built.Test results show that the module can receive parallel signals at 30Gbit/s.The sensitivity of the module is -13.6dBm for 1E-13BER.

  • An Optoelectronic Pulse Frequency Modulation Circuitfor Retinal Prosthesis

    Liu Jinbin, Chen Hongda, Gao Peng, Pei Weihua, Sui Xiaohong

    Chin. J. Semicond.  2006, 27(4): 700

    Abstract PDF

    A pulse frequency modulation(PFM) circuit for retinal prosthesis,which generates electrical pulses with frequency proportional to the intensity of incident light,is presented.The fundamental characteristic of the circuit is described and analyzed.The circuit is realized in 0.6μm CMOS process,and the simulation results testify to the possibility of sub-retinal implantation.

  • Photolithography Process Simulation for Integrated Circuitsand Microelectromechanical System Fabrication

    Zhou Zaifa, Huang Qing'an, Li Weihua

    Chin. J. Semicond.  2006, 27(4): 705

    Abstract PDF

    Simulations of photoresist etching,aerial image,exposure,and post-bake processes are integrated to obtain a photolithography process simulation for microelectromechanical system(MEMS) and integrated circuit(IC) fabrication based on three-dimensional (3D) cellular automata(CA).The simulation results agree well with available experimental results.This indicates that the 3D dynamic CA model for the photoresist etching simulation and the 3D CA model for the post-bake simulation could be useful for the monolithic simulation of various lithography processes.This is determined to be useful for the device-sized fabrication process simulation of IC and MEMS.

  • Characteristics of Ge-Dots/Si Multilayered Structure Fabricatedby Ni-Based Metal Induced Lateral Crystallization

    Yan Bo, Zhang Kuangji, Shi Yi, Pu Lin, , Han Ping, Zhang Rong

    Chin. J. Semicond.  2006, 27(4): 712

    Abstract PDF

    We report a novel method for obtaining high-density Ge-dots/Si multilayered structures by combining low-pressure chemical vapor deposition and metal-induced lateral crystallization.High density self-assembled Ge-dots/a-Si multilayered structures are first deposited on SiO2/Si (100) substrates using low-pressure chemical vapor deposition,and then a-Si layers are crystallized by low-temperature (below 550℃) Ni-based metal-induced lateral crystallization.Optical micrograph,electron microscopy, and micro-Raman spectroscopy observations show that the lateral crystallization Si regions have large leaf-like grains (about 4~5μm in diameter) elongated along the metal-induced lateral crystallization direction with (110) preference.The strain shift of Ge dots reveals the formation of a high quality interface between the crystallized Si and Ge dots.

  • Ultrafast Absorption Spectra of Nanocrystal ZnSe Material

    Huang Shihua, Lu Fang

    Chin. J. Semicond.  2006, 27(4): 717

    Abstract PDF

    Using a modified solvothermal method in which potassium borohydride is employed as a reducing reagent,nanocrystal ZnSe materials are prepared in a triethylamine solvent.Compared to bulk ZnSe,nanocrystal ZnSe has a blue shift in its steady absorption edge.The degree of this blue shift increases with the decrease of nanocrystal particle size,as a result of quantum confinement effects.The ultrafast absorption spectra of ZnSe nanocrystals indicate that the electron-electron scattering time is 8.74ps and 2.77ps for the average nanocrystal size of 75 and 45nm,respectively.With the decrease of the size of nanocrystal,the probability of inelastic collision among carriers and nanocrystal surface increases,resulting in the enhancement of the carrier-phonon coupling strength and the shortening of the carrier-photon scattering time.

  • Metal-Induced Grown Poly-SiGe by SiGe Heteroepitaxy on Ni Disilicide

    Wu Guibin, Ye Zhizhen, Zhao Xing, Liu Guojun, Zhao Binghui

    Chin. J. Semicond.  2006, 27(4): 721

    Abstract PDF

    Poly-SiGe films are prepared using a metal-induced growth technique with an ultrahigh vacuum chemical vapor deposition (UHVCVD) system at low temperatures.The crystal quality and surface morphology of the poly-SiGe films are characterized by XRD and SEM.The influences of various growth parameters on the surface morphology of the poly-SiGe films are investigated.It is shown that when the growth temperature is above 510℃,Ni has a great effect on the poly-SiGe growth.Uniform films are obtained at 10Pa,while densely packed SiGe whiskers are formed when adopting a low-high pressure growth mode

  • Dispersion Effect on Double-Layer Anti-Reflection Coatingsof GaAs Solar Cells

    Bai Yiming, Chen Nuofu, Dai Ruixuan, Wang Peng, Peng Changtao

    Chin. J. Semicond.  2006, 27(4): 725

    Abstract PDF

    The dispersion effect of double-layer (DL) anti-reflection coatings (ARCs) is considered.The reflectance of DL SiO2/ZnSe and the SiO2/ZnS ARCs as a function of wavelength and weighted reflectance for SiO2 top anti-reflection coatings with different thicknesses in GaAs solar cells are calculated according to the optical interference matrix.The resulting curves are compared to those without dispersion effect.The results show that the dispersion effect noticeably influences the reflectance of DL ARCs,especially in the spectral range from 300 to 500nm.Moreover,different effects are displayed in different DL ARCs.Compared to those without dispersion effect,the minimal weighted reflectance of SiO2/ZnSe DL ARCs increases from 1.14% to 1.55%,while that of SiO2/ZnS DL ARCs decreases from 1.49% to 1.46%.

  • Breakdown Voltage Analysis of a REBULF LDMOS Structurewith an n+-Floating Layer

    Zhang Bo, Duan Baoxing, Li Zhaoji

    Chin. J. Semicond.  2006, 27(4): 730

    Abstract PDF

    A novel REBULF (reduced bulk field) concept is proposed for the development of a smart power integrated circuit with a thin epitaxy layer,and a new REBULF LDMOS device structure is designed with an n+-floating layer embedded in the high-resistance substrate.The mechanism of the improved breakdown characteristics is that a high electric field around the drain is reduced by a n+-floating layer,which causes the redistribution of the bulk electric field in the drift region,and the substrate supports more biases.The critical condition of the REBULF,which is analyzed and validated by a 2D MEDICI simulator,is that the product of the location of the n+-floating layer and the substrate doping cannot exceed 1E12cm-2. The breakdown voltage of the REBULF LDMOS is 75% greater than that of a RESURF LDMOS.

  • Current Simulation Based on the Percolation-Like Conductionin Ultra-Thin Gate Oxides After Soft Breakdown

    Wang Yangang, Xu Mingzhen, Tan Changhua, Duan Xiaorong

    Chin. J. Semicond.  2006, 27(4): 735

    Abstract PDF

    The characteristics of the gate current (Ig) and substrate current (Ib) of ultra-thin gate oxides (≤3nm) after soft breakdown (SBD) are studied.An analytic formula for Ig and Ib after SBD--the percolation-like conduction (PLC) formula, based on the percolation-like mechanism, is proposed.The post SBD current-voltage relationship of Ig and Ib in a larger voltage range (-4~+3V) is simulated with the PLC formula,which is simple for the study of ultra-thin gate oxide reliability.

  • 1.55μm InP-InGaAsP Quantum-Well Lasers Fabricatedon Si Substrates by Wafer Bonding

    Yu Lijuan, Zhao Hongquan, Du Yun, Huang Yongzhen

    Chin. J. Semicond.  2006, 27(4): 741

    Abstract PDF

    1.55μm InP-InGaAsP quantum-well lasers are fabricated on Si substrates by wafer bonding.The laser structures are designed and grown by MOCVD and bonded to Si wafers The laser are then fabricated on the bonded thin films.Room-temperature operation is achieved for 20μm-wide mesa lasers with a threshold current of 160mA and an output power of 10mW at 350mA.

  • Fabrication of Optical Waveguide Devices with UV-Writing Technology

    Wu Yuanda, Xia Junlei, An Junming, Li Jianguang, Wang Hongjie, Hu Xiongwei

    Chin. J. Semicond.  2006, 27(4): 744

    Abstract PDF

    The photosensitivity of commercial Si/SiO2 waveguide materials prepared by PECVD is studied.After exposure to high-pressure hydrogen,the as-deposited films are irradiated with excimer-laser pulses operating at 248nm.The change in the induced relative refractive index is about 0.34%.The sectional index distribution of UV-writing waveguides is investigated in detail.Finally,single-mode optical waveguides and Y-splitters are fabricated from silica-based planar optical waveguides with UV-writing technology with a silicon mask.The test results agree with the simulation results.

  • Polymeric Thermo-Optic Digital Optical Switches

    Liang Kun, Chen Wang, Wu Boyu, Luo Shuyun, Yin Jianjun, Ye Gang

    Chin. J. Semicond.  2006, 27(4): 747

    Abstract PDF

    The organic polymeric 2×2 digital optical switches taking advantages of the electro-optic and the thermo-optic effects are studied and fabricated.At a 1.31μm optical communication wavelength,the typical digital behavior of the thermo-optic polymeric switch is demonstrated.

  • Analysis of Coupling Efficiency of TO-Packaged VCSELs

    Liu Chao, Wang Xin, Yuan Haiqing, Zhong Baoxuan, Zhu Ninghua

    Chin. J. Semicond.  2006, 27(4): 751

    Abstract PDF

    The dependences of TO-packaged VCSELs on packaging subassemblies are analyzed using FRESNEL and MATLAB softwares.It is found that the coupling efficiency can be improved by increasing the refractive index of the coupling lens and by decreasing the height of the TO-cap or the size of the coupling lens.

  • Analysis and Fabrication of Torsion Micromirror ActuatorsBased on a MEMS Technology

    Li Sihua, Liu Yufei, Gao Xiang, Wu Yaming

    Chin. J. Semicond.  2006, 27(4): 756

    Abstract PDF

    Based on micro-electro-mechanical systems,a novel method employing bonding and wafer thinning technologies is proposed and demonstrated to fabricate torsion micromirror actuators with dimensions of 600μm×700μm.The experimental results show that a tilt angle of about 0.3. is achieved under a driving voltage of 18V with a resonator frequency over 1kHz.

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