bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of Reducing Shallow Trench Isolation Mechanical Stress on Active Length for 40 nm n-Type Metal–Oxide–Semiconductor Field-Effect Transistors
Authors: Huang Yao-Tsung , Wu San-Lein , Lin Hau-Yu , Kuo Cheng-Wen , Chang Shoou-Jinn , Hong De-Gong , Wu Chung-Yi , Huang Cheng-Tung , Cheng Osbert
Published: April 2011

We report an improved densification annealing process for sub atmospheric chemical vapor deposition (SACVD)-based shallow trench isolation (STI) to enhance n-type metal–oxide–semiconductor field-effect transistor (nMOSFET) performance for 40 nm node and beyond. Experimental results show that this improved STI densification process leads to lower compressive stress in the small active area compared with the standard STI process. This is beneficial to electron mobility and leads to an enhancement of on-current (I
ON). Moreover, comparable drain induced barrier lowering (DIBL) and subthreshold swing (SS) characteristics for both devices indicate that the improved densification process would no significant influences on process variations or dopant diffusions. Hence, the improved STI process can be adopted in 40 nm complementary metal–oxide–semiconductor (CMOS) technology and beyond.
Conduction Mechanism and Reliability Characteristics of a Metal–Insulator–Metal Capacitor with Single ZrO2 Layer
Authors: Kwon Hyuk-Min , Han In-Shik , Park Sang-Uk , Bok Jung-Deuk , Jung Yi-Jung , Shin Hong-Sik , Kang Chang-Yong , Lee Byoung-Hun , Jammy Raj , Lee Ga-Won , Lee Hi-Deok
Published: April 2011

In this paper, the electrical characteristics and reliability of ZrO2-based metal–insulator–metal (MIM) capacitors are investigated. High capacitance density of 15.3 fF/µm2 was achieved for ZrO2 MIM capacitors, which is acceptable for the reported MIM capacitors. Schottky emission at the low field region is not a dominant mechanism, and Frenkel–Poole emission is the dominant mechanism at the high electric field region. The extracted dynamic constant and trap energy level were 4.013 and 0.963 eV, respectively. The reduced trap energy level with increasing electric field is due to a rise in the field-induced barrier-lowering effect. The variation of α as a function of stress time under constant voltage stress (CVS) gradually decreases, while the variation of ΔC
stress/C
0 under CVS increases because the generation of new dipoles in the high-κ dielectric under CVS may cause charge trapping in the high-κ dielectric.
Improving Read Disturb Characteristics by Using Double Common Source Line and Dummy Switch Architecture in Multi Level Cell NAND Flash Memory with Low Power Consumption
Authors: Kang Myounggon , Park Ki-Tae , Song Youngsun , Lim Youngho , Suh Kang-Deog , Shin Hyungcheol
Published: April 2011

Two new NAND structures using double common source line (CSL) and dummy switch and their read operation schemes as a solution for NAND flash memories have been proposed. Compared with conventional scheme, the proposed read schemes improves read disturb characteristics beyond sub-30 nm technology node. By using proposed read scheme, the number of fail bits of proposed NAND was decreased than those of conventional NAND at read cycles. Also, it was proven that they contribute to improve the performance and suppress the power consumption. The proposed NAND was verified by both simulation and experimental measurements in a fabricated 40 nm multi level cell (MLC) NAND device.
Dynamics of the Charge Centroid in Metal–Oxide–Nitride–Oxide–Silicon Memory Cells during Avalanche Injection and Fowler–Nordheim Injection Based on Incremental-Step-Pulse Programming
Authors: Fujiki Jun , Haimoto Takashi , Yasuda Naoki , Koyama Masato
Published: April 2011

In this study we have carried out a precise analysis on transient charge centroid dynamics during the programming of metal–oxide–nitride–oxide–silicon (MONOS) memory cells. Using the incremental-step-pulse programming (ISPP) scheme, the charge centroid is exactly extracted during the programming. Furthermore, avalanche injection enables low-field carrier injection, making it easy to identify the accessible trap sites in the charge trap layer. Avalanche injection is also used to study the field dependence of available traps. From this analysis, the charge centroid of MONOS memory is found to move from the tunnel layer/charge layer interface to the charge layer/block layer interface during low-field programming. In contrast, the location of the charge centroid is limited to the charge layer/block layer interface when the Fowler–Nordheim (FN) injection is used for programming at a high electric field. Furthermore, the low-electric-field programming achieves a high capture efficiency owing to a larger flatband shift in this programming than in high-electric-field programming. Therefore, low-electric-field programming is desired to increase the trap site availability and carrier capture efficiency.
Investigation of Threshold Voltage Disturbance Caused by Programmed Adjacent Cell in Virtual Source/Drain NAND Flash Memory
Authors: Kim Wandong , Kwon Dae Woong , Ji Jung Hwan , Lee Jung Hoon , Lee Jong-Ho , Shin Hyungcheol , Park Byung-Gook
Published: April 2011

In this paper, we investigate the threshold voltage disturbance caused by programmed adjacent cells in virtual source/drain (VSD) NAND flash memory device. The fringing field induced by charge in an adjacent memory node inhibits the inversion of virtual source/drain region. So, it increases the threshold voltage of the read cell. This is a drawback for the multi-level cell (MLC) operation. The device simulation and measurement data of fabricated devices show that the disturbance increases as the cell gate length and VSD length decreases. It can be minimized by the electric field concentration induced by the arch shape structure.
Ferroelectric-Gate Thin-Film Transistor Fabricated by Total Solution Deposition Process
Authors: Miyasako Takaaki , Trinh Bui Nguyen Quoc , Onoue Masatoshi , Kaneda Toshihiko , Tue Phan Trong , Tokumitsu Eisuke , Shimoda Tatsuya
Published: April 2011

We have fabricated inorganic ferroelectric-gate thin-film transistors (FGTs) using only a chemical solution deposition (CSD) process. All layers, including the LaNiO3 (LNO) gate electrode, Pb(Zr,Ti)O3 (PZT) ferroelectric-gate insulator, indium–tin-oxide (ITO) source/drain electrodes, and ITO channel, were formed on a SrTiO3 (STO) substrate by the CSD process. We obtained a local epitaxially grown PZT/LNO perovskite heterostructure with good crystalline quality and no interfacial layer. The fabricated FGT exhibited typical n-channel transistor operation, with a counterclockwise hysteresis loop due to the ferroelectric nature of the PZT-gate insulator, and also exhibited good drain current saturation in output characteristics. These properties are equivalent to or better than those obtained with FGTs fabricated by means of conventional vacuum processes. The obtained on/off current ratio, memory window, and subthreshold voltage swing were about 106, 2.5 V, and 357 mV/decade, respectively.
Phenomenological Model for Stress and Relaxation Processes of Resistance Drift in Magnetic Tunnel Junctions
Authors: Kamakura Yoshinari , Nakano Shinsuke , Taniguchi Kenji
Published: April 2011

A phenomenological model for the resistance drift of AlOx-based magnetic tunnel junctions (MTJs) is proposed. The viscoelastic deformation of the MTJ system stressed under high-density current is modeled by considering the superposition of many Kelvin–Voigt components with various time constants. The model reproduces well the degradation and the recovery characteristics of the MTJ resistance observed in various stress experiments.
A Novel Ni/WOX/W Resistive Random Access Memory with Excellent Retention and Low Switching Current
Authors: Chien Wei-Chih , Chen Yi-Chou , Lee Feng-Ming , Lin Yu-Yu , Lai Erh-Kun , Yao Yeong-Der , Gong Jeng , Horng Sheng-Fu , Yeh Chiao-Wen , Tsai Shih-Chang , Lee Ching-Hsiung , Huang Yu-Kai , Chen Chun-Fu , Kao Hsiao-Feng , Shih Yen-Hao , Hsieh Kuang-Yeu , Lu Chih-Yuan
Published: April 2011

The behavior of WO
X
resistive random access memory (ReRAM) is a strong function of the top electrode material, which controls the conduction mechanism and the forming process. When using a top electrode with low work function, the current conduction is limited by space charges. On the other hand, the mechanism becomes thermionic emission for devices with a high work function top electrode. These (thermionic) devices are also found to have higher initial resistance, reduced forming current, and larger resistance window. Based on these insights and considering the compatibility to complementary metal–oxide–semiconductor (CMOS) process, we proposed to use Ni as the top electrode for high performance WO
X
ReRAM devices. The new Ni/WO
X
/W device can be switched at a low current density less than 8×105 A/cm2, with RESET/SET resistance ratio greater than 100, and extremely good data retention of more than 300 years at 85 °C.
Microstructural Characterization in Reliability Measurement of Phase Change Random Access Memory
Authors: Bae Junsoo , Hwang Kyuman , Park Kwangho , Jeon Seongbu , Kang Dae-hwan , Park Soonoh , Ahn Juhyeon , Kim Seoksik , Jeong Gitae , Chung Chilhee
Published: April 2011

The cell failures after cycling endurance in phase-change random access memory (PRAM) have been classified into three groups, which have been analyzed by transmission electron microscopy (TEM). Both stuck reset of the set state (D0) and stuck set of the reset state (D1) are due to a void created inside GeSbTe (GST) film or thereby lowering density of GST film. The decrease of the both set and reset resistances that leads to the tails from the reset distribution are induced from the Sb increase with cycles.
Characteristics and the Model of Resistive Random Access Memory Switching of the Ti/TiO2 Resistive Material Depending on the Thickness of Ti
Authors: Kim Sook Joo , Sung Min Gyu , Joo Moon Sig , Kim Wan Gee , Kim Ja Yong , Yoo Jong Hee , Kim Jung Nam , Gyun Byun Ggu , Byun Jun Young , Roh Jae Sung , Park Sung Ki , Kim Yong Soo
Published: April 2011

The effects of the reactive Ti layer on the resistive switching characteristics of TiN/Ti/TiO2/TiN resistive random access memory (ReRAM) are investigated. Nitridation at the top region of Ti during reactive sputtering of the TiN layer and oxygen gettering of Ti from TiO2 make the TiON/TiO2-x
interface. It results in TiO2 with a higher concentration of oxygen vacancies during metal alloy annealing, resulting in the low-initial-resistance state. This leads to a stable bipolar switching after the first set process. A larger thickness of Ti decreases resistance value in the high-resistance state, which enables the adjustment of on/off resistance ratio.
Impedance Analysis of Controlled-Polarization-Type Ferroelectric-Gate Thin Film Transistor Using Resistor–Capacitor Lumped Constant Circuit
Authors: Fukushima Tadahiro , Maeda Kazuhiro , Yoshimura Takeshi , Ashida Atsushi , Fujimura Norifumi
Published: April 2011

We propose a novel ferroelectric-gate field-effect transistor using a polar oxide semiconductor channel, which is called a controlled-polarization (CP)-type ferroelectric-gate thin film transistor (TFT). Although the CP-type ferroelectric-gate TFTs with a ZnO/YMnO3structure shows nonvolatile memory operation, the relationship between the electrical characteristics of the TFTs and the direction of spontaneous polarization of the ferroelectric layer (PSFe) below the channel has not been revealed. In this study, the direction ofPSFeis analyzed by the impedance spectra of the channel conductance because it can be expected that the channel conductance depends on the direction of thePSFe. The five conditions of the channel conductance are assumed and the impedances between the source electrode and the gate electrode of each condition are calculated by SPICE. The direction ofPSFeat various gate voltages is determined by the comparison of the calculated results and experimental results. It was found that the channel conductance of the ferroelectric-gate TFT has steep change by the change of the direction ofPSFe.
A 5.4–9.2 GHz 19.5 dB Complementary Metal–Oxide–Semiconductor Ultrawide-Band Receiver Front-End Low-Noise Amplifier
Authors: Azhari Afreen , Kubota Shinichi , Toya Akihiro , Sasaki Nobuo , Kikkawa Takamaro
Published: April 2011

In this work, we present an ultrawide-band (UWB) complementary metal–oxide–semiconductor (CMOS) low-noise amplifier (LNA) for wireless communication in the upper UWB band, that is, from 5.4–9.2 GHz bandwidth with a wide-band 50 Ω input matching network in front of the LNA. A three-stage cascode-topology-based LNA with high-transconductance MOS transistors, was employed to improve the voltage gain up to 23 dB at 7.5 GHz, with 4.5–9.2 GHz 3 dB bandwidth. The maximum output power S
21 was 19.5 dB at 7.3 GHz, with 5.4–9.2 GHz 3 dB bandwidth. The input matching circuit was designed with a reduced number of passive elements, resulting in an input reflection coefficient S
11 of less than -10 dB from 4.5–9.2 GHz. The noise figure of the LNA was as low as 3.5 dB and the input-referred third-order intercept point (IIP3) was -8 dBm. The LNA has output reflection coefficient S
22 of less than -10 dB from 5–7 GHz and a good reverse isolation, that is, S
12 of < -45 dB in the entire UWB, due to a cascode topology. The LNA was fabricated using 180 nm CMOS technology, which consumes 56 mW power at 1.8 V power supply. In this paper, we also demonstrate a wireless communication of 7 GHz Gaussian monocycle pulse (GMP) by horn antennas and the LNA from 20 cm transmission distance.
A 26 GHz Transceiver Chipset for Short Range Radar Using Post-Passivation Interconnection
Authors: Ujita Shinji , Kawai Yasufumi , Kaibara Kazuhiro , Negoro Noboru , Fukuda Takeshi , Sakai Hiroyuki , Ueda Tetsuzo , Tanaka Tsuyoshi
Published: April 2011

We demonstrate a 26 GHz SiGe bipolar complementary metal oxide semiconductor (BiCMOS) transceiver chipset for short-range spread-spectrum (SS) radar system. The integrated frequency triplers lower the local oscillation frequency down to 8.8 GHz, and eliminate the carrier leak in the transmitting signal which enables high sensitivity. The on-chip balun connected to the mixer demodulating by the pseudo noise (PN) code in the receiver increases the dynamic range of the receiving signal. Low-loss transmission lines on Si substrate are fabricated by post-passivation interconnection process using thick benzocyclobutene (BCB). We have confirmed the transmitting signal having spread-spectrum with suppressing the carrier leak, the improvement of the dynamic range of the receiver, and the reduction of the transmission loss on Si substrate. We have demonstrated the operation of the 26 GHz ultra wide band (UWB) SS radar, corresponding to detecting a human located at 7 m away from the system.
Non-volatile Random Access Memory and NAND Flash Memory Integrated Solid-State Drives with Adaptive Codeword Error Correcting Code for 3.6 Times Acceptable Raw Bit Error Rate Enhancement and 97% Power Reduction
Authors: Fukuda Mayumi , Higuchi Kazuhide , Takeuchi Ken
Published: April 2011

This paper proposes the adaptive codeword error correcting code (ECC) for non-volatile random access memory (NV-RAM) and NAND flash memory-integrated solid state drive (SSD). In the proposed SSD, NV-RAM such as resistive random access memory (ReRAM), phase change random access memory (PRAM) and magneto resistive random access memory (MRAM) is used as write buffers. The NV-RAM write buffer compensates the 10–100 times speed gap between the NAND flash memory and the SSD interface and realizes the 10 Gbps write. During the write, data are first stored in NV-RAM at 10 Gbps. Then, data in NV-RAM are transferred to the NAND flash memory with the sustained write speed of 2.69 Gbps. During the read, the read data output from the NAND flash memory to the controller by bypassing NV-RAM. At the 10 Gbps write, the proposed SSD decreases the power consumption by 97%. In the proposed adaptive codeword ECC, errors of both NV-RAM and the NAND flash memory are corrected without circuit area overhead. The ECC codeword, the data unit where ECC is performed, is adaptively optimized for NV-RAM and the NAND flash memory. As a result, the acceptable raw bit error rate before ECC increases by 3.6 times without ECC circuit area or power consumption penalty compared with the single ECC scheme where the single ECC circuits correct errors of both NV-RAM and the NAND flash memory.
Source/Drain Engineering for In0.7Ga0.3As N-Channel Metal–Oxide–Semiconductor Field-Effect Transistors: Raised Source/Drain with In situ Doping for Series Resistance Reduction
Authors: Gong Xiao , Chin Hock-Chun , Koh Shao-Ming , Wang Lanxiang , Zhu Ivana , Wang Benzhong , Chia Ching Kean , Yeo Yee-Chia
Published: April 2011

In this paper, we report N-channel metal–oxide–semiconductor field-effect transistors (N-MOSFETs) featuring in situ doped raised In0.53Ga0.47As source/drain (S/D) regions. This is the first demonstration of such regrowth on an In0.7Ga0.3As channel. After SiON spacer formation, the raised In0.53Ga0.47As S/D structure was formed by selective epitaxy of In0.53Ga0.47As in the S/D regions by metal-organic chemical-vapor deposition (MOCVD). In situ silane SiH4 doping was also introduced to boost the N-type doping concentration in the S/D regions for series resistance R
SD reduction. The raised S/D structure contributes to I
Dsat enhancement for the In0.7Ga0.3As N-MOSFETs.
High-Gain and High-Bandwidth AlGaN/GaN High Electron Mobility Transistor Comparator with High-Temperature Operation
Authors: Kwan Alex Man Ho , Wong King Yuen , Liu Xiaosen , Chen Kevin J.
Published: April 2011

This paper presents the dc and dynamic characterizations of a GaN-based voltage comparator, fabricated with monolithic integration of enhancement-mode (E-mode) and depletion-mode (D-mode) AlGaN/GaN high electron mobility transistors (HEMTs). The comparator features high gain (>31 dB) and wide bandwidth (>4 MHz), and small propagation delay time (<20 ns) over a wide temperature range up to 250 °C. Its dc gain is still 27.1 dB at 400 °C. These results demonstrate the potential of the AlGaN/GaN HEMT technology for mixed-signal integrated circuits used in GaN power electronics that promises high-voltage, high-current, and high-temperature operation.
ZnO Thin Films Fabricated by Plasma-Assisted Atomic Layer Deposition
Authors: Kawamura Yumi , Hattori Nozomu , Miyatake Naomasa , Horita Masahiro , Uraoka Yukiharu
Published: April 2011

We investigated zinc oxide (ZnO) thin films prepared by plasma-assisted atomic layer deposition (PA-ALD), and thin film transistors (TFTs) with the ALD ZnO channel layer for application to next-generation displays. The dependences of the electrical characteristics of the fabricated TFTs on the plasma condition were evaluated. The plasma injection time dependence of the transfer characteristics, the refractive index, and the impurity concentration revealed that insufficient oxidation degrades the performance of ZnO TFTs. On the basis of the experimental results, high-performance ZnO TFTs can be obtained by PA-ALD at a low temperature.
New Stacked Metal–Insulator–Metal Capacitor with High Capacitance Density for Future InP-Based ICs
Authors: Tsutsumi Takuya , Sugitani Suehiro , Nishimura Kazumi , Ida Minoru
Published: April 2011

Increasing the capacitance density would be a very effective way of making InP IC chips smaller because capacitors occupy a large area of InP IC chips. In this study, as a way of increasing capacitance density, we propose new stacked metal–insulator–metal (MIM) capacitors that can be fabricated by using only two additional masks alternately and repeatedly. The capacitors can also be fabricated with a short turn-around time by forming side contact via, which allows each MIM electrode to connect to each other electrically all at once. In the proposed capacitors with five stacked layers, the capacitance density increases by a factor of 5, from 0.30 to 1.47 fF/µm2, when 175-nm-thick SiN is used. The leakage current level is the same as that of a single-layer MIM capacitor.
Analysis of the Nonlinear Optical Parameter of ZnO Channel Waveguides
Authors: Teraoka Edgar Yoshio Morales , Kita Tomohiro , Broaddus Daniel H. , Tsukazaki Atsushi , Kawasaki Masashi , Gaeta Alexander L. , Yamada Hirohito
Published: April 2011

In this paper, we analyze the nonlinear optical parameter γ estimated from experimental results of spectral broadening in ZnO channel waveguides. The effective area was calculated for waveguides of various dimensions and using the resulting data, the nonlinear optical parameter γ was obtained analytically. We compare these values with those estimated from measurements, and found good agreement between them. We extended the analysis to calculate the optimal size for maximum nonlinearity and found that the fabricated waveguides were very close to the optimal size.
Epitaxial Lateral Overgrowth of Gallium Nitride for Embedding the Micro-Mirror Array
Authors: Ku Hao Ming , Huang Chen Yang , Liao Chen Zi , Chao Shiuh
Published: April 2011

We report here details of the epitaxial lateral overgrowth (ELOG) process for embedding a Ta2O5/SiO2 multilayer high reflector micro-mirror array (MMA) in the GaN. The process was aiming for purpose of applying the MMA on the micro-light emitting diode (micro-LED) for light extraction enhancement of the micro-LED. A two-step ELOG process with different temperature and pressure to achieve high lateral growth rate and low vertical growth rate was implemented and the two-step ELOG process was followed by a slow growth rate process to complete embedding the MMA.
Excited State Bilayer Quantum Dot Lasers at 1.3 µm
Authors: Majid Mohammed A. , Childs David T. D. , Shahid Hifsa , Chen Siming C. , Kennedy Kenneth , Airey Robert J. , Hogg Richard A. , Clarke Edmund , Spencer Peter , Murray Ray
Published: April 2011

We report the realization of excited state bilayer quantum dot (QD) lasers in the 1.31 µm region. The higher saturated gain and lower scattering time of the excited states of the ensemble of QDs offers the opportunity for high modulation bandwidths. Gain measurements for these structures are discussed and compared to conventional QD laser structures. The extension of QD ground state operating wavelengths to 1.45 µm spanning the O- and E-band is also demonstrated.
Effects of the Hole Tunneling Barrier Width on the Electrical Characteristic in Silicon Quantum Dots Light-Emitting Diodes
Authors: Kim Tae-Youb , Park Nae-Man , Choi Cheol-Jong , Huh Chul , Ahn Chang-Geun , Sung Gun Yong , You In-Kyu , Suemitsu Maki
Published: April 2011

Electrical properties of the Silicon quantum dots (Si-QD) light-emitting diodes (LEDs), in its dependence on the nitrogen source used in the silicon nitride (SiN
x
) matrix growth, have been studied. Si-QDs are formed in-situ during the SiN
x
film growth, and no post-annealing process for crystallization was applied. To confirm the electrical properties of the Si-QD devices, we manufacture the Si-QD LED. Both p-type and p+-type Si substrate were tested in role of hole tunneling in the LED performance. The high-resolution transmission electron microscopy (HRTEM) analyses and the current–voltage (I–V) measurement show that the Si-QDs embedded in the SiN
x
grown with ammonia (NH3) are located at the interface between the SiN
x
film and the Si substrate. This is related to the observed increase in the forward current by considering a decrease in the hole tunneling barrier width between the Si substrate and the Si-QDs.
Design and Simulation of Silicon Ring Optical Modulator with p/n Junctions along Circumference
Authors: Amemiya Yoshiteru , Ding Hao , Yokoyama Shin
Published: April 2011

A Si ring optical modulator, where a low operation voltage is expected, is proposed. In this device, p/n junctions are arranged along the circumference of the ring resonator. By simulation, the propagation loss <5 dB/cm and 1×1017–5×1017 cm-3 carrier concentration are estimated to be necessary, to obtain >95% modulation at 1 V, where the length of the p/n region is 150 nm. Multi-interference occurs between the light reflections at the interfaces of neutral and depletion regions. When the resonance wavelength of multi-interference is equal to that of the ring resonator, the effect of multi-interference is simulated. Moreover, it is shown that the multi-interference effect is not the problem when a different resonance wavelength is used as an input optical signal.
A Study of Mach–Zehnder Interferometer Type Optical Modulator Applicable to an Accelerometer
Authors: Suzuki Masato , Takahashi Tomokazu , Aoyagi Seiji , Amemiya Yoshiteru , Fukuyama Masataka , Yokoyama Shin
Published: April 2011

A novel Mach–Zehnder interferometer (MZI)-type optical modulator based on micro electro mechanical systems (MEMS) technology is developed in this study. In this optical modulator, one of two branched waveguides in the MZI has a floating beam structure (air-bridge type). Additionally, a cantilever supporting a proof mass intersects with the floating optical waveguide. When an inertial force due to acceleration is applied to the proof mass, the floating waveguide is expanded and the output of the MZI is modulated. Therefore, this optical modulator will be applicable to an accelerometer in the future. To decrease optical loss at the intersectional point between the floating waveguide and the cantilever in the MZI, the multi-mode interference (MMI) waveguide is serially connected with the floating waveguide and the cantilever crosses to the MMI waveguide. An optimization of the MMI waveguide and an estimation of deflection of the floating waveguide due to applying force are carried out by using optical and mechanical simulation, respectively. The proposed optical modulator is fabricated by inductively coupled plasma (ICP) etching of the top layer of a silicon-on-insulator (SOI) wafer, which is made of crystal Si. The floating waveguide in the modulator is formed by removal of its underlying buried oxide (BOX) layer of SOI. As a result of evaluation, we have succeeded in changing the output of the MZI by applying a force to the cantilever. However, the modulation is smaller than the expected value. Improvement of the modulation and detection of the inertial force due to the applied acceleration are future tasks.
A Semiconductor Soliton Cavity Laser Diode and its Output Characteristics
Authors: Shih Ming Chang , Chen Cheng Sen
Published: April 2011

We demonstrated the fabrication of a novel semiconductor laser diode with a cavity formed by a spatial soliton waveguide based on the photovoltaic photorefractive effect. The laser diode device is fabricated on a metal organic chemical vapor deposition (MOCVD)-grown InGaAlP multiple-quantum-well structure with a ridge-waveguide circular ring resonator and a Y-junction directional coupler section. The optical properties of the soliton waveguide can be effectively modulated by the emission from the circular ring resonator and the coupling of the Y-junction directional coupler. The laser diode showed the hybrid output spectral characteristics of a single-mode spectrum with a peak at 658 nm and a multimode spectrum distributed at a shorter wavelength at the nonwaveguide soliton cavity terminal. In addition, experiments to investigate the effect of the soliton cavity length were performed to reveal the mechanism of the lasing threshold and the output characteristics of the soliton cavity laser diode.
Estimating the Junction Temperature of InGaN and AlGaInP Light-Emitting Diodes
Authors: Lee Ya-Ju , Lee Chia-Jung , Chen Chih-Hao
Published: April 2011

The junction temperature of light-emitting diodes (LEDs) directly and significantly affects LEDs performances. Thus, accurate measurement and precise estimation of LEDs junction temperature become extremely important. In this study, we analyze the physical foundation of temperature-dependent electrical characteristics and develop a new scheme to directly express the dependence of junction temperature on injected current for InGaN and AlGaInP LEDs. From a more general viewpoint, our scheme for the estimation of junction temperature is primarily based on the LEDs external properties, and therefore can be applied to other kinds of III–V compound-based semiconductor LEDs.
GaN-Based Metal–Semiconductor–Metal Ultraviolet Photodetectors with the ZrO2Insulating Layer
Authors: Chen Chin-Hsiang , Tsai Yu-Hsuan , Tsai Sung-Yi , Cheng Chung-Fu
Published: April 2011

GaN metal–semiconductor–metal (MSM) ultraviolet (UV) photodetectors (PDs) with ZrO2insulating layers were successfully fabricated and characterized. It was found that we can achieve a small dark current and large photocurrent to dark current contrast ratio from the proposed devices with the use of ZrO2insulating layers. With a 20 V applied bias, it was found that the leakage current of the fabricated MSM PDs with ZrO2insulating layers was 1.73 ×10-10A. This small leakage current should be attributed to the large barrier height caused by the insertion of the ZrO2insulating layers. We can also achieve a large UV to visible rejection ratio from the PDs with ZrO2insulating layers. Furthermore, it was also found that we can significantly reduce noise equivalent power and enhance detectivity by using ZrO2insulating layers.
Optical Crossing and Integration Using Hybrid Si-Wire/Silica Waveguides
Authors: Wakayama Younosuke , Kita Tomohiro , Yamada Hirohito
Published: April 2011

We studied the feasibility of an integrated optical circuit consisting of Si-wire waveguides and silica-based waveguides. In order to realize such a hybrid waveguide optical circuit, we investigated a waveguide junction structure based on adiabatic mode conversion with tapered Si and a waveguide crossing structure of heterogeneous waveguides by numerical analysis and measurements. We estimated the optical coupling loss between the waveguides to be 0.39 dB from the measurements. We also estimated the insertion loss of the waveguide crossing to be less than 0.7 dB, and the crosstalk between the waveguides to be less than -35 dB by numerical analysis.
Luminescence Characteristics and Annealing Effect of Tb-Doped AlBNO Films for Inorganic Electroluminescence Devices
Authors: Masumoto Keiko , Semba Akitoshi , Kimura Chiharu , Taniguchi Takashi , Watanabe Kenji , Sakata Takao , Aoki Hidemitsu
Published: April 2011

Inorganic electroluminescence (EL) devices have attracted attention because of their application in low-power-consumption displays. However, the operating voltage of inorganic EL devices is very high. We have investigated AlBNO films as host materials of the luminescence layer to lower the operating voltage. Moreover, the investigation used Tb as the luminescence center because Tb3+ ions show green luminescence that has a high luminous coefficient. Tb-doped AlBNO films were deposited by RF magnetron sputtering. Cathodoluminescence and photoluminescence show the luminescence due to f–f transition of Tb3+ ions. The luminescence can be attributed to both the energy transfer from the host material to the Tb3+ ions and the direct excitation of Tb3+ ions. In addition, we achieved a drastic increase in the luminescence by an annealing treatment due to an increase in Tb3+ ions and the homogeneous dispersion of Tb atoms. Therefore, AlBNO films could be used for inorganic EL devices.
Transmission Electron Microscopy and Raman-Scattering Spectroscopy Observation on the Interface Structure of Graphene Formed on Si Substrates with Various Orientations
Authors: Handa Hiroyuki , Takahashi Ryota , Abe Shunsuke , Imaizumi Kei , Saito Eiji , Jung Myung-Ho , Ito Shun , Fukidome Hirokazu , Suemitsu Maki
Published: April 2011

Graphene can be grown on three major low-index substrates of Si(111), (110), and (001) by forming a 3C-SiC thin film and by subliming Si atoms from the top few layers of the SiC film. We have investigated the structure of graphene/3C-SiC interface by cross-sectional transmission electron microscopy (XTEM) and Raman-scattering spectroscopy. While the interface layer quite similar to that on the graphene/6H-SiC(0001) face is found to exist on the 3C-SiC(111)/Si(111) substrate, no such interface structure exists on the (110)- and (001)-oriented faces.
Improvement of Rectifying Property in Pt/TiOx/Pt by Controlling Oxidization of TiOx Layer
Authors: Zhong Ni , Shima Hisashi , Akinaga Hiro
Published: April 2011

Rectifying Pt/TiO
x
/Pt capacitors have been prepared by depositing a single TiO
x
layer. An Ohmic contact is always found at TiO
x
/Pt (bottom electrode, BE), and is attributed to the formation of a dead layer at the beginning of the deposition process. The current–voltage (I–V) characteristic is governed by the transport characteristic of TiO
x
/Pt (top electrode, TE). The rectifying property is only found in Pt/TiO
x
/Pt with the TiO
x
layer when the O2 working flow is high during the deposition process. Besides a high O2 flow, a high working pressure is also required. Moreover, postannealing treatment can improve the rectifying property of the capacitors. Upon the optimization of the postannealing treatment process, the rectifying ratio at ±1.0 V increases from 20 to 4 ×103.
Structural Changes Caused by Quenching of InAs/GaAs(001) Quantum Dots
Authors: Takahasi Masamitu , Fujikawa Seiji
Published: April 2011

Self-assembled InAs/GaAs(001) quantum dot structures before and after quenching were investigated by in situ X-ray diffraction to assess the effects of quenching. Before quenching, quantums dots were uniform in size so that the shape and internal lattice constant distribution of a quantum dot were quantitatively determined on the basis of three-dimensional X-ray intensity mapping. X-ray measurements after quenching revealed that the quantum dot size showed a bimodal distribution as a result of the proliferation of dislocated islands during quenching. A formula to describe the X-ray diffraction from dislocated islands with a large size distribution is presented. The cooling rate between 20 and 40 K/min was found to have little effect on the structures of quenched quantum dots.
High-Temperature Annealing Effect of Si in Group-V Ambient Prior to Heteroepitaxy of InAs in Metal–Organic Vapor Phase Epitaxy
Authors: Deura Momoko , Kondo Yoshiyuki , Takenaka Mitsuru , Takagi Shinichi , Shimogaki Yukihiro , Nakano Yoshiaki , Sugiyama Masakazu
Published: April 2011

We investigated the state of the Si(111) surface and its effect on InAs growth after annealing at high temperature with and without an As or P source flow in H2 ambient in metal–organic vapor phase epitaxy (MOVPE). In multi-step growth of InGaAs by micro-channel selective-area growth, perfect coverage of Si growth areas by InAs, which is grown first, by controlling the state of the Si surface is critical for the following InGaAs lateral growth. Although both As and P sources protect the surface against contamination from inside the reactor, annealing with the P source at high temperature is optimal in terms of InAs nucleation and coverage of growth areas by InAs. The amount of O contamination after P annealing at high temperature was significantly lower than that under other annealing conditions. Therefore, O is the most critical contamination in InAs nucleation.
Application of Droplet Elimination Process by Radical-Beam Irradiation to InGaN Growth and Fabrication of InN/InGaN Periodic Structure
Authors: Yamaguchi Tomohiro , Umeda Hidetomo , Araki Tsutomu , Nanishi Yasushi
Published: April 2011

A growth method, named droplet elimination by radical-beam irradiation (DERI), consisting of a metal-rich growth process (MRGP) and a droplet elimination process (DEP), was developed for the growth of InGaN ternary alloys. In the MRGP using the growth of InGaN under a metal-rich condition [N*/(In+Ga)<1], Ga was preferentially incorporated into the growing InGaN and In was forced out to the surface. This In was transformed to epitaxial InN on top of the InGaN underlayer in the DEP using a subsequent nitrogen radical-beam irradiation. By repeating the MRGP and DEP, an InN/InGaN periodic structure was successfully fabricated.
Reduction of S-parameter by the Introduction of Nitrogen in GaNAs: Positron Annihilation and Photoluminescence Spectroscopy Study
Authors: Nakamoto Hiroki , Ishikawa Fumitaro , Kondow Masahiko , Ohshima Yushi , Yabuuchi Atsushi , Mizuno Masataka , Araki Hideki , Shirai Yasuharu
Published: April 2011

We study the annealing behavior of GaNAs by positron annihilation spectroscopy and photoluminescence spectroscopy. The introduction of nitrogen reduces the S-parameter of the material, which is further lowered by annealing. Moreover, the samples show typical optical characteristics of the GaNAs system. The results suggest that the observed reduction of the S-parameter is not simply due to the reduction of vacancy-type defects, but could be related to the characteristic carrier localization in this material system.
Growth of Semipolar InN(1013) on LaAlO3(112) Substrate
Authors: Chen Wei-Chun , Tian Jr-Sheng , Wang Wei-Lin , Ho Yen-Teng , Chang Li
Published: April 2011

In this study, we report the growth and characterization of semipolar (1013) InN films grown on LaAlO3(112) substrate by metalorganic molecular beam epitaxy. InN films were grown at various substrate temperatures in the range of 465–540 °C. Structural and optical properties of semipolar InN were investigated by high resolution X-ray diffraction, scanning electron microscopy, and photoluminescence measurements. The results show that semipolar (1013) InN layers can be grown at 510 °C with the full-width at half maximum of the X-ray rocking curve about 1400 arcsec and electron mobility of 494 cm2 V-1 s-1.
Graphite Thin Films Consisting of Nanograins of Multilayer Graphene on Sapphire Substrates Directly Grown by Alcohol Chemical Vapor Deposition
Authors: Miyasaka Yuta , Nakamura Atsushi , Temmyo Jiro
Published: April 2011

Graphene has been attracting a strong interest as a transparent electrode as well as a THz nanoelectronic device owing to its unique properties. To date, large-area graphene growth has been realized by chemical vapor deposition (CVD) with a catalyst metal. To avoid the transfer of segregated graphene, we have examined directly graphite thin film growth on nonpolar a-sapphire substrates without any catalyst metal by alcohol CVD. Graphite thin films consisting of nanograins of multilayer graphene on a-sapphire substrates were verified by a combination of transmission electron spectroscopy (TEM), and Raman analyses, and optical transparent and sheet resistance measurements.
Facile Phase Transfer of Gold and Au-Core/Ag-Shell Nanoparticles from Aqueous to Toluene Solution Using Alkylamine Molecules and Their Assemblies on Solid Supports
Authors: Sugawa Kosuke , Tanoue Yoshimasa , Tanaka Daido , Sakai Tatsuya
Published: April 2011

Surface plasmons induced at metal surfaces generate remarkable enhancements of localized electric fields as a result of interactions with incident light fields. This is called localized surface plasmon resonance (LSPR). In this study, we report a simple technique for transferring LSPR-active gold and Aucore–Agshell nanoparticles from an aqueous to a toluene phase using octadecylamine molecules for organic-solution processing. The changes in optical properties and size dependence of transfer behavior of the nanoparticles were evaluated by absorption spectroscopy and transmission electron microscopy (TEM). The upper limit of the size of particles that can be transferred into an organic phase is about 25 nm. We also fabricated an LSPR-active colloidal monolayer film on a solid support by solvent evaporation of a colloidal organic solution.
Degradation Mechanism for Continuous-Wave Green Laser-Crystallized Polycrystalline Silicon n-Channel Thin-Film Transistors under Low Vertical-Field Hot-Carrier Stress with Different Laser Annealing Powers
Authors: Wang Mu-Chun , Yang Hsin-Chia , Hsu Hong-Wen , Hsieh Zhen-Ying , Chen Shuang-Yuan , Chang Shih-Ying , Liu Chuan-Hsi
Published: April 2011

For a thin-film transistor (TFT) in a display, the hot-carrier (HC) effect still plays an important role in causing the degradation of source/drain (S/D) current and reflects the problem of reliability. In this study, the proposed TFT devices were treated by continuous-wave green laser annealing on their Si-channels and also activated by the thermal-furnace method. Furthermore, using the shifts of capacitance–voltage (C–V) curves and observing the curve variation before and after stress, the targeted number of interface states and bulk traps in a channel can be realized. Indirectly, the degradation level of the tested device can be quantified when the stressed drain voltage is indicated in the horizontal direction, the gate voltage is slightly larger than the threshold voltage and is labeled in the vertical direction, and both are applied. The critical mechanism in degradation involves the location and number of interface states and grain boundary traps. These traps are mainly attributed to the interface states between SiO2 and channel polycrystalline silicon, the grain boundary traps, and the grain traps.
Polarized Thermoreflectance and Reflectance Study of ReS2 and ReS2:Au Single Crystals
Authors: Huang Tung-Pai , Lin Der-Yuh , Kao Yu-Cheng , Wu Jyun-De , Huang Ying-Sheng
Published: April 2011

In this article, we present the optical study of undoped and Au-doped rhenium disulphide (ReS2 and ReS2:Au) using temperature- and polarization-dependent thermoreflectance (PTR) and reflectance (R) measurements. We have observed the indirect band gaps (E
g||
, E
g⊥), and direct band-edge excitonic transitions (E
1
ex, E
2
ex, E
3
ex and E
4
ex) at various polarization angles. The amplitudes of E
1
ex and E
2
ex transitions have an orthogonal characteristic and follow the Malus rule. A small blue-shift of indirect band gaps has been observed for the ReS2:Au sample, we believe that this result is contributed from the doping effects. We also measured the temperature-dependent PTR spectra in the temperature range from 55 to 300 K, and determined the temperature dependences of the transition energies and broadening parameters of E
1
ex and E
2
ex transitions. Reflectance measurements at various polarizations have been performed to confirm our observations.
Singlet–Triplet Mixing Due to g-Factor Mismatch in Double Quantum Dot
Authors: Takahashi Ryo , Kono Kimitoshi , Tarucha Seigo , Ono Keiji
Published: April 2011

Two electron spins form the spin singlet or triplet state if these spins have the same g-factor value, or a mix state consisting of both the singlet and triplet states if these spins have different g-factor values. It is considered that two energy levels of electrons are formed in a double quantum dot device for use in quantum information processing; however, the g-factors of the electrons have not been treated as an important factor because they cannot be changed easily in experiments. We introduce a numerical calculation method for the singlet–triplet mix state due to the g-factor mismatch in double quantum dots. It is found that this mismatch changes the energy levels of the original singlet and triplet states; thus, it affects the intersecting points of the energy levels of the singlet and triplet states where a dynamic nuclear polarization appears via hyperfine interaction.
Admittance Measurement for a Quantum Point Contact in a Multiterminal Quantum Hall Device
Authors: Washio Kazuhisa , Hashisaka Masayuki , Kamata Hiroshi , Muraki Koji , Fujisawa Toshimasa
Published: April 2011

We present admittance measurements for a quantum point contact embedded in a multiterminal quantum Hall system, using a time-resolved technique. The real part of ac admittance agrees well with conventional dc conductance, while the imaginary part shows a crossover between inductive and capacitive admittance, as theoretically predicted in the low-frequency limit. Multiterminal measurements with different chiralities of edge channels ensure that possible extrinsic coupling is negligibly small. The characteristic capacitance in our device is estimated from dependence of the imaginary part on the frequency.
Simulation Study of Charge Modulation in Coupled Quantum Dots in Silicon
Authors: Kambara Tomohiro , Kodera Tetsuo , Takahashi Tsunaki , Yamahata Gento , Uchida Ken , Oda Shunri
Published: April 2011

We have calculated electron states in a lithographically defined Si double quantum dot (DQD) device. Electrons are confined near the upper interface in the silicon-on-insulator (SOI) layer by top gate and side gate voltages. Surface charge density, N
S, at 4 K in DQDs is evaluated using experimental data of the gate voltage dependence of N
S in a metal–oxide–semiconductor (MOS) transistor at 100 and 4 K. With optimum side gate biases, electrons are confined in QDs and coupling between QDs is controlled in a few-electron regime. We have also proposed that a charge sensor is required to read out the few-electron regime because no current flows in the DQD device.
Effects of Interface Grading on Electronic States and Optical Transitions in GaSb Type-II Quantum Dots in GaAs
Authors: Kawazu Takuya , Sakaki Hiroyuki
Published: April 2011

Electronic states in type-II GaSb quantum dots (QDs) in GaAs are studied theoretically and compared with experiments to clarify how the spatial overlap of holes in the dot and electrons outside is affected by the interface grading caused by the interdiffusion of Sb and As. Cone-shaped QDs with the initial size of 6 nm height and 20 nm radius are analyzed. The wavefunctions of electrons and holes and their overlap Θ are calculated. In an initial stage of grading, when the grading length L
g is below 1.2 nm, the mixing occurs only near the dot/matrix interface, leading to a decrease in Θ, since holes are squeezed into a smaller volume whereas electrons are more repelled by the dot. In later stages where L
g exceeds 1.2 nm, however, the hole confinement and the electron repulsion by the dot both weaken, leading to an increase in Θ; this accounts for a recent finding that the annealing of GaSb QDs induces a blue shift and an intensity increase in photoluminescence spectra.
Improved Characteristics of Metal Organic Chemical Vapor Deposition-Grown ZnO Thin-Film Transistors by Controlling VI/II Ratio of ZnO Film Growth and Using a Modified Thin-Film Transistor Layer Structure
Authors: Remashan Kariyadan , Choi Yong-Seok , Park Seong-Ju , Jang Jae-Hyung
Published: April 2011

Thin-film transistors (TFTs) were fabricated on glass substrates using ZnO channel layers grown with two VI/II (oxygen/diethylzinc) ratios of 25,000 and 100,000 by metal organic chemical vapor deposition (MOCVD). The ZnO TFTs employing the channel grown with a VI/II ratio of 25,000 exhibit a field-effect mobility (µFE) of 4.3 cm2 V-1 s-1, a subthreshold slope (SS) of 1.3 V/dec, and an on/off current ratio of 9×107. On the other hand, ZnO TFTs using the channel grown with a higher VI/II ratio of 100,000 exhibit a µFE of 2.1 cm2 V-1 s-1, an SS of 0.64 V/dec, and an on/off current ratio of 1×108. The improvement in SS and the reduction in µFE are respectively attributed to the lower growth rate and smaller grain size of the ZnO film. The ZnO TFTs fabricated by using the higher-VI/II-ratio-grown ZnO layer together with a thin MOCVD-grown MgZnO layer at the channel/gate insulator interface exhibit high performance, and their µFE, SS, and on/off current ratio are 8.9 cm2 V-1 s-1, 0.42 V/dec, and 3×108, respectively. This is the best performance reported to date for ZnO TFTs that are realized on glass substrates with MOCVD-grown channel layers. The superior performance of ZnO TFTs with the MgZnO layer is ascribed to the larger grain size of the ZnO film and the better channel/gate insulator interface.
Light Enhancement of Silicon-Nanocrystal-Embedded SiOx Film on Silicon-on-Insulator Substrate
Authors: Chen Cheng-Chang , Lin Yung-Hsaing , Shih M. H. , Lin Gong-Ru , Kuo Hao-Chung
Published: April 2011

We reported the light enhancement from a silicon-nanocrystal-embedded SiO
x
film on a silicon-on-insulator (SOI) substrate in the visible light range. The light emission from the annealed SiO
x
film is one order stronger than the emission from a nonannealed SiO
x
film. Compared with the SiO
x
film on a Si substrate, two-fold enhancement in light emission from the SiO
x
film on a SOI substrate was also observed. The enhancement was attributed to better vertical confinement of optical field in the SiO
x
film on a SOI substrate.