bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature Dependence of Gate Current and Breakdown Behaviors in an n+-GaAs/p+-InGaP/n--GaAs High-Barrier Gate Field-Effect Transistor
Authors: Yu Kuo-Hui , Lin Kun-Wei , Cheng Chin-Chuan , Chang Wen-Lung , Tsai Jung-Hui , Cheng Shiou-Ying , Liu Wen-Chau
Published: October 2002

The temperature dependence of gate current and breakdown behavior in an n+-GaAs/p+-InGaP/n--GaAs high-barrier gate field-effect transistor has been studied and demonstrated. Due to the presence of an n+-GaAs/p+-InGaP/n--GaAs high-barrier gate structure, the device shows high-breakdown characteristics. In addition, we found that the off-state breakdown voltage BV
DS is dominated by channel and gate breakdowns at T=300 to 420 K, and gate current I
G comes mainly from the tunneling mechanism within this temperature range. However, as the temperature is increased above 420 K, the I
G is seriously affected by the substrate leakage current and BV
DS is only dominated by gate breakdown.
Deposition of ZnO Thin Films by the Ultrasonic Spray Pyrolysis Technique
Authors: Lee Youngjin , Kim Hagbong , Roh Yongrae
Published: October 2002

This paper describes the design of an ultrasonic spray pyrolysis system and the determination of the optimal conditions for deposition of ZnO thin films. The film is desired to have strong piezoactivity, high resistivity, and good thickness uniformity. Zinc acetate is the source solution for the ZnO film on top of a SiO2/Si wafer. Controlled experiments show that the zinc acetate solution of 0.05 mol% doped with 30 at.% of LiCl can provide good ZnO films at the substrate temperature of 420°C. The optimal substrate rotation rate and nozzle tilting angle are also determined to improve the uniformity of the film. ZnO thin films deposited with these conditions show good c-axis orientation, and a resistivity higher than 107 Ω·cm after annealing in oxygen, and good thickness uniformity across a 4′′ substrate wafer. Properties of the ZnO film developed in this study are comparable to those obtained with conventional techniques.
Evaporation and Expansion of Poly-tetra-fluoro-ethylene Induced by Irradiation of Soft X-Rays from a Figure-8 Undulator
Authors: Osamu Maida Osamu Maida , Norinao Kohma Norinao Kohma , Masato Ueno Masato Ueno , Akira Shibuya Akira Shibuya , Takeshi Kanashima Takeshi Kanashima , Masanori Okuyama Masanori Okuyama , Haruhiko Ohashi Haruhiko Ohashi
Published: October 2002

The effects of soft X-ray irradiation of poly-tetra-fluoro-ethylene (PTFE) have been investigated using a figure-8 undulator. In the case of high-intensity irradiation, the surface temperature of the irradiated region increased and PTFE near the surface was evaporated effectively. In contrast, the PTFE surface swelled by the under low-intensity irradiation with the insertion of Al filters more than 9 µm thick. This reaction was found to be strongly dependent on the flux. The surface profile is largely determined by the relationship between fragment desorption and porous structure generation, and an increase in the surface temperature enhances the fragment desorption and has considerable influence on the surface profile. Al filter insertion decreases the flux and suppresses low-energy photons which are absorbed near the surface. Hence irradiated photons are composed of high-energy photons which penetrate deeply, and the surface temperature is difficult to increase by Al-filter-inserted irradiation.
Surface Images of SiO2/Si(100) Pattern using Electron Emission Microscopy with Metastable Atoms, Photons and Low-Energy Electrons
Authors: Yasufuku Hideyuki , Okumura Masao , Ibe Takahiro , Okudaira Koji K. , Harada Yoshiya , Ueno Nobuo
Published: October 2002

The surface images of a SiO2 pattern on Si(100) was observed by three types of electron emission microscopies, i.e., metastable electron emission microscopy (MEEM) with metastable He, photoelectron emission microscopy (PEEM) and low-energy electron emission microscopy (LEEM). Among these, MEEM gave the most diffused image at the pattern edges of the SiO2 region. Furthermore, it is found that the difference in MEEM, LEEM and PEEM images can provide new information on the spatial distribution of surface electronic states. By comparing MEEM, LEEM and PEEM images, it is expected that we can obtain local information on surface electronic states in more detail.
Growth of Undoped ZnO Films with Improved Electrical Properties by Radical Source Molecular Beam Epitaxy
Authors: Ken Nakahara Ken Nakahara , Tetsuhiro Tanabe Tetsuhiro Tanabe , Hidemi Takasu Hidemi Takasu , Paul Fons Paul Fons , Kakuya Iwata Kakuya Iwata , Akimasa Yamada Akimasa Yamada , Koji Matsubara Koji Matsubara , Ralf Hunger Ralf Hunger , Shigeru Niki Shigeru Niki
Published: October 2002

High-quality undoped ZnO epitaxial films with mobilities as high as 120 cm2V-1s-1 and carrier concentrations as low as 7.6 ×1016 cm-3 have been grown on (1120) a-sapphire substrates using low-temperature buffer layers, a slow substrate cooling process and a modified oxygen radical cell. Pole figure measurements reveal that a-plane sapphire substrates are effective for the elimination of 30° rotation domains, which usually appear in the case of ZnO growth on c-sapphire. The low-temperature buffer layers allow high-temperature growth, because initial ZnO growth does not occur with high initial growth temperature. The use of slow substrate cooling prevents the deterioration of the electrical properties of the ZnO films. Use of quartz insulators in the oxygen radical cell eliminates aluminum contamination, which is a serious problem when using conventional alumina insulators.
A Novel T-Shaped Shallow Trench Isolation Technology
Authors: Hong Sug Hun , Ahn Dong Ho , Park Moon Han , Kang Ho Kyu
Published: October 2002

This paper describes a novel T-shaped shallow trench isolation (STI) technology, which has the same effective isolation length with conventional STI but significantly reduced aspect ratio. The T-shaped STI is formed using 2-step trench etches. After the formation of the 1st trench of a relatively low aspect ratio, oxide spacer is formed inside the trench sidewall. And the 2nd trench is made to ensure an effective isolation length. When T-shaped STI is filled with undoped silicate glass (USG) and high density plasma (HDP) oxide, the mouth of 2nd trench is closed by the overhang of filling materials so that the effective aspect ratio of T-shaped STI can be lowered. We evaluated the electrical characteristics of T-shaped STI. Also, we performed simulation of the stress distribution and the junction profile. T-shaped STI has shown comparable characteristics to conventional STI and no electrical or physical degradation was found. We have adopted this technology to 512 Mbit flash memory (0.5 µm cell pitch) and obtained excellent structural and electrical properties. In addition, we obtained the excellent gap filling ability even for the 1 Gbit flash memory (0.34 µm cell pitch) and beyond.
Channel Width Dependence of Mobility in Ge Channel Modulation-Doped Structures
Authors: Irisawa Toshifumi , Miura Hidetoshi , Ueno Tetsuji , Shiraki Yasuhiro
Published: October 2002

We systematically studied channel width dependence of mobility in Ge channel modulation- doped structures fabricated by solid-source molecular beam epitaxy using the low-temperature buffer technique. This technique made it possible to obtain high-quality strain-relaxed Si1-x
Ge
x
buffer layers having a very smooth surface (∼5 nm). It was found that the mobility had a maximum around the channel width (W
ch) of 7.5 nm and that it reached 13000 cm2/Vs at 20 K and 1175 cm2/Vs at room temperature (RT). The decrease in mobility with decreasing channel width was attributed to interface roughness scattering, since its influence increased as W
ch decreased. On the other hand, the decrease in mobility for wider channels was considered to come from strain relaxation of Ge channel layers. In fact, high-resolution X-ray diffraction measurements revealed that strain relaxation of Ge channel layers occurred in the sample with W
ch=20 nm. By lowering the growth temperature of Ge channel layers to suppress the strain relaxation, the mobility of 1320 cm2/Vs at RT was achieved.
Ultrashallow Junction Formation for Sub-100 nm Complementary Metal-Oxide-Semiconductor Field-Effect Transistor by Controlling Transient Enhanced Diffusion
Authors: Ohuchi Kazuya , Adachi Kanna , Murakoshi Atsushi , Hokazono Akira , Kanemura Takahisa , Aoki Nobutoshi , Nishigohri Masahito , Suguro Kyoichi , Toyoshima Yoshiaki
Published: October 2002

The annealing process of implantation damage that induces transient enhanced diffusion during a
subsequent thermal process such as low-pressure chemical vapor deposition (LPCVD) is optimized from the viewpoint of the process integration of an 80 nm physical gate length complementary metal-oxide-semiconductor field-effect transistor (CMOSFET) device. For nMOSFETs, a temperature as high as 960°C is necessary to prevent transient enhanced diffusion. In contrast, for pMOSFETs, higher temperature annealing promotes thermal diffusion instead of preventing enhanced diffusion. It is found that a separate annealing process sequence is required. In utilizing preamorphization implantation prior to boron implantation, however, higher temperature annealing is effective for forming an ultrashallow junction. Consequently, the annealing processes can be performed simultaneously.
Ultrashallow and Low-Leakage p+n Junction Formation by Plasma Immersion Ion Implantation (PIII) and Low-Temperature Post-Implantation Annealing
Authors: Kanemoto Kei , Aharoni Herzl , Ohmi Tadahiro
Published: October 2002

p+n junctions are fabricated by the combination of BF3 plasma immersion ion implantation (PIII) and low-temperature post-implantation annealing. Ultrashallow junctions and very low leakage currents (∼10-11 A at -1 V in 1 mm2 junctions) have been obtained. Despite the fact that the activation of the PIII layer is not sufficient, the I–V characteristics obtained are comparable to those of junctions formed by conventional ion implantation. By a combination of Si+ preamorphization and BF3 PIII aimed to improve the dopant activation, a maximum surface concentration of activated boron higher than 1020 cm-3 is obtained in 550°C annealing for p+n junctions with 5 nm depth. The leakage currents, however, are increased by the Si+ implantation in low-temperature post-implantation annealing.
A New High Speed Switching Bipolar Power Transistor with Corrugated Base Junctions
Authors: Park Chanho , Lee Kwyro
Published: October 2002

A new structure of the bipolar power transistor with corrugated base junctions is proposed for fast switching applications. The proposed bipolar power transistors with corrugated base junctions are fabricated without any additional process steps. We investigated the electrical characteristics of the transistor such as current gain, saturation voltages between the collector and the emitter and turn-off transient times, and compared them with those of the conventional bipolar transistors with parallel plane base junctions. It is shown that the bipolar transistors with corrugated base junctions have not only shallow saturation but also built-in field accelerating the recombination of excess electrons and holes in the base region. The storage times of the bipolar power transistors with corrugated base junctions are shorter by above 25% than those of the conventional bipolar power transistors.
A Low Voltage Actuated Microelectromechanical Switch for RF Application
Authors: Hah Dooyoung , Yoon Euisik , Hong Songcheol
Published: October 2002

A push-pull operation is proposed for low voltage actuation of a microelectromechanical (MEM) switch for RF application. The push-pull operation realized by torsion springs and contact electrode height amplification by leverage, lowers the actuation voltage of the MEM switch by reducing the gap between actuation electrodes. The proposed MEM switch is fabricated by gold surface micromachining. Switching operation up to 4 GHz is demonstrated. The actuation voltage is as low as 5 V. The insertion loss of ∼1 dB and the isolation as high as ∼40 dB at 1 GHz are achieved by the push-pull operation.
Design and Optimization of Novel High Responsivity, Wideband Silicon Photodiode
Authors: Swe Toe Naing , Yeo Kiat Seng , Chew Kok Wai , Chu Sanford
Published: October 2002

Various types of proposed photodiodes fabricated using a 0.25 µm complementary metal oxide semiconductor (CMOS) technology are presented. The effects of different design layouts on the performance are compared for a wide range of light intensity, photodiode current, dark current and diode capacitance. Frequency response of these devices are also characterized and compared for different bias conditions. A high responsivity photodiode having a 3 dB bandwidth of 9.4 GHz at a reverse bias voltage of 5 V is demonstrated. The results show that the proposed photodiodes outperform the best silicon photodiodes reported so far.
Novel High-Radiance Surface-Emitting Light Emitting Diode Structure with Circular 45° Corner Reflector and Microlens
Authors: Park Eun-Hyun , Kim Moon-Jung , Cha Jung-Ho , Kwon Young-Se
Published: October 2002

A new type of light-emitting diode(LED) with a circular 45° corner reflector and microlens is proposed and fabricated. The improvement of light output power of the proposed LED structure is calculated and compared with that of the conventional surface-emitting LED type. A microlens is fabricated on LED using the UV curing method. The HBr–H3PO4–K2Cr2O7 chemical etchant is developed for fabricating the circular 45° corner reflector. The measured light-current curve of the proposed LED shows that, compared to conventional LEDs, the output power increases considerably at high current level and the linearity is significantly improved by the circular 45° corner reflector. From the spectra measurement, we can confirm that the proposed LED structure shows combined characteristics of both conventional surface- and edge-emitting LEDs.
High-Brightness Wafer-Bonded Indium-Tin Oxide/Light-Emitting Diode/Mirror/Si
Authors: Horng Ray-Hua , Lien Yi-Chung , Peng Wei-Chih , Wuu Dong-Sing , Tseng Chung-Yang , Seieh Chi-Hua , Huang Man-Fang , Tsai Shi-Jen , Liu Jin-Shiarng
Published: October 2002

Indium-tin oxide (ITO) used as the window layer and current-spreading layer for wafer-bonded AlGaInP/mirror/Si light-emitting diodes (MS LEDs) has been reported. The ITO films prepared by sputtering have low resistivity (2.1×10-4 Ω-cm) and high transmittance (>90% in the visible region). The MS LEDs incorporating the ITO layer and In/ITO provide higher light output than ITO-free MS LEDs. They also exhibit a linear increase of a uniform distributed light output without radiation saturation as the injection current increases. Moreover, the MS LED, ITO/MS LED and ITO/In/MS LEDs provide 2.8, 3.0 and 3.4 times improvement in external power efficiency, respectively, as compared with the absorbing-substrate LED fabricated from the same AlGaInP LED wafer. Due to the inserted In layer that reduces the contact resistance between ITO and the GaAs contact layer without causing obvious absorption of the emitting light, the ITO/In/MS LEDs can achieve the highest power conversion efficiency among the LEDs studied.
Optical Absorption Rate Determination, on the Front Facet of High-Power GaAs Laser Diodes, by Means of Thermoreflectance Technique
Authors: Schaub Emmanuel
Published: October 2002

Very-high-resolution thermoreflectance measurements have been used to study the light absorption occurring on the front facet of GaAs laser diodes, which is responsible for their damage. We determined the activation of the induced surface heat source for an injected current higher than the laser emission threshold current. This varying thermal behavior of the laser diode according to the value of the injected current has been used to determine the contribution to heat dissipation due to the surface source only. By identification using a thermal model we could evaluate for the first time the surface absorption rate both on coated and noncoated laser diodes. We propose it as a new reliability criterion, which enables discrimination of laser diodes both according to their coating and to their aging.
In Situ X-Ray Photoelectron Spectroscopy Study of Etch Chemistry of Methane-Based Reactive Ion Beam Etching of InP Using N2
Authors: Jin Zhi , Hashizume Tamotsu , Hasegawa Hideki
Published: October 2002

The effects of nitrogen gas on the methane-based reactive ion beam etching (RIBE) of InP were studied in detail. The surface was very rough and covered with In droplets and heavy polymer when it was etched by the mixture of CH4/H2 without nitrogen gas. In contrast, the surface smoothness was improved markedly when nitrogen gas was added, realizing a root mean square (RMS) roughness comparable to that of the initial InP surface before etching. From the detailed X-ray photoelectron spectroscopy (XPS) analysis, it was found that the formation of P–N bonds on the surface could suppress the preferential evaporation of P atoms in the PH3 form and balance the In- and P-reactions during the etching process. This resulted in the decrease of In droplets and a smoother etched InP surface. It was also found that the rate limiting process for etching was the In-related reaction. The study of Raman scattering showed that the crystal quality of the etched surface was improved when N2 gas was added to the CH4/H2 mixture.
Bulk and Interface Deep Levels in InGaP/GaAs Heterostructures Grown by Tertiarybutylphosphine-Based Gas Source Molecular Beam Epitaxy
Authors: Ishikawa Fumitaro , Hirama Atsushi , Hasegawa Hideki
Published: October 2002

InGaP/GaAs heterostructures were grown by gas source molecular beam epitaxy (GSMBE) using tertiarybutylphosphine (TBP), and their bulk and interface deep levels were studied by deep level transient spectroscopy (DLTS), photoluminescence (PL), and cathodoluminescence (CL) techniques. Five bulk deep levels related to phosphorus vacancies and their complexes were detected by DLTS. They could be almost completely removed under a TBP flow rate higher than 4–5 sccm, accompanied by a marked increase of the bulk band edge PL intensity. On the other hand, InGaP/GaAs heterostructures grown under high TBP flow rates showed anomalous PL and CL peaks near 1.7 eV. CL study performed by changing the acceleration voltage showed that these peaks were heterointerface related, most likely due to phosphorus vacancies near interfaces. InGaP/GaAs quantum wells (QW) without such peaks and with intense QW emission were successfully formed by avoiding phosphorous vacancy formation through elimination of growth interruption.
Evidence of Enlarged Drift Length in Nanocrystalline Porous Silicon Layers by Time-of-Flight Measurements
Authors: Kojima Akira , Koshida Nobuyoshi
Published: October 2002

The electron transport mechanism of nanocrystalline porous silicon (PS) has been studied for a self-supporting PS layer by a time-of-flight (TOF) measurement. The observed TOF transient photocurrent curves are different from those of both single crystalline silicon (c-Si) and amorphous silicon (a-Si). On the basis of the mobility-lifetime product (µτ) deduced from TOF measurements, it is shown that the electron drift length of PS is enhanced up to 3.8 µm at 100 K and 2.6 µm at 300 K.
Analog Computation Using Quantum-Dot Cell Network
Authors: Wu Nan-Jian , Saito Kazuyuki , Yasunaga Hitoshi
Published: October 2002

A novel analog-computation system using a quantum-dot cell network is proposed to solve complex problems. Analog computation is a promising method for solving a mathematical problem by using a physical system analogous to the problem. We designed a novel quantum-dot cell consisting of three-stacked quantum dots and constructed a cell network utilizing the nearest-neighbor interactions between the cells. We then mapped a graph 3-colorability problem onto the network so that the single-electron configuration of the network in the ground state corresponded to one of the solutions. We calculated the ground state of the cell network and found solutions to the problems. The results demonstrate that analog
computation is a promising approach for solving complex problems.
Memory Operation of InAs Quantum Dot Heterostructure Field Effect Transistor
Authors: Son Heesoo , Kim Junggun , Kim Moondeock , Hong Songcheol
Published: October 2002

The memory operation of a self-assembled InAs quantum dot heterostructure field effect transistor (FET) is presented. The amount of trapped electrons in the quantum dots determines the gate-source capacitance and the drain current at a gate bias. In capacitance–voltage (C–V) measurement at low frequency, the quantum dots respond to the signal and a difference of capacitance was observed. These results imply that the memory operation is due to the charge trapping effect of InAs quantum dots.
Charge Trapping in SiOx/ZrO2 and SiOx/TiO2 Gate Dielectric Stacks
Authors: Houssa Michel , Naili Mohamed , Heyns Marc , Stesmans Andre
Published: October 2002

The generation of traps in SiO
x
/ZrO2 and SiO
x
/TiO2 gate dielectric stacks during gate voltage stress of metal-oxide-semiconductor capacitors is investigated. The trap generation rate and trap cross section are extracted from the analysis of the gate current increase observed during the electrical stress. These data can be explained by a model based on a two-stage degradation process, i.e., (1) H+ generation in the high-permittivity gate dielectric layer by the injected electrons and (2) transport of H+ in the high permittivity material, resulting in bond breaking and generation of ZrOH or TiOH neutral centers. The threshold electron energy for H+ generation and the activation energy for H+ transport and bond breaking are extracted from fits to the experimental results.
Influence of Organic Contaminant on Breakdown Characteristics of MOS Capacitors with Thin SiO2
Authors: Takenobu Yoshino Takenobu Yoshino , Shin Yokoyama Shin Yokoyama , Tsukuru Suzuki Tsukuru Suzuki , Toshiaki Fujii Toshiaki Fujii
Published: October 2002

The feasibility of practical application of a plastic wafer box with a UV/photoelectron cleaning unit has been investigated. The total ion chromatogram spectra showed a dramatic decrease of the organic contaminant adsorbed on Si wafers stored in the newly developed plastic box made of polyether sulfone (PES) to which the UV/photoelectron cleaning unit is attached. We also found that the organic contaminant on the Si surface strongly enhances the appearance of a soft breakdown of oxide films of metal-oxide-semiconductor (MOS) capacitors, resulting in a decreased reliability of the gate oxide. However, the injected charge at which the gate oxide undergoes the final hard breakdown is significantly improved by attaching the UV/photoelectron cleaning unit to the PES wafer box.
A Single Chip Automotive Control LSI Using SOI Bipolar Complimentary MOS Double-Diffused MOS
Authors: Kawamoto Kazunori , Mizuno Shoji , Abe Hirofumi , Higuchi Yasushi , Ishihara Hideaki , Fukumoto Harutsugu , Watanabe Takamoto , Fujino Seiji , Shirakawa Isao
Published: October 2002

Using the example of an air bag controller, a single chip solution for automotive sub-control systems is investigated, by using a technological combination of improved circuits, bipolar complimentary metal oxide silicon double-diffused metal oxide silicon (BiCDMOS) and thick silicon on insulator (SOI). For circuits, an automotive specific reduced instruction set computer (RISC) center processing unit (CPU), and a novel, all integrated system clock generator, dividing digital phase-locked loop (DDPLL) are proposed. For the device technologies, the authors use SOI-BiCDMOS with trench dielectric-isolation (TD) which enables integration of various devices in an integrated circuit (IC) while avoiding parasitic miss operations by ideal isolation. The structures of the SOI layer and TD, are optimized for obtaining desired device characteristics and high electromagnetic interference (EMI) immunity. While performing all the air bag system functions over a wide range of supply voltage, and ambient temperature, the resulting single chip reduces the electronic parts to about a half of those in the conventional air bags. The combination of single chip oriented circuits and thick SOI-BiCDMOS technologies offered in this work is valuable for size reduction and improved reliability of automotive electronic control units (ECUs).
Low Voltage Operation of Nonvolatile Metal-Ferroelectric-Metal-Insulator-Semiconductor (MFMIS)-Field-Effect-Transistors (FETs) Using Pt/SrBi2Ta2O9/Pt/SrTa2O6/SiON/Si Structures
Authors: Tokumitsu Eisuke , Okamoto Kojiro , Ishiwara Hiroshi
Published: October 2002

We report p-channel metal-ferroelectric-metal-insulator-semiconductor (MFMIS)-field-effect-transistors (FETs) which can operate at a voltage as low as 3.5 V using Pt/SrBi2Ta2O9/Pt/SrTa2O6/SiON/Si structures. It is shown that the use of the saturated P–E hysteresis loop is effective to improve the data retention time. To utilize the saturated P–E loop, MFMIS-FETs with a large S
M/S
F ratio are fabricated. We demonstrate the nonvolatile memory function of the p-channel MFMIS-FETs with a memory window of 1.5 V, operating at ±3.5 V. It was also found that the fabricated MFMIS-FETs have fairly good data retention characteristics.
Low-Temperature Preparation of Ferroelectric Sr2(Ta1-x,Nbx)2O7 Thin Films by Pulsed Laser Deposition and Their Application to Metal-Ferroelectric- Insulator-Semiconductor-FET
Authors: Toshiyuki Nakaiso Toshiyuki Nakaiso , Minoru Noda Minoru Noda , Masanori Okuyama Masanori Okuyama
Published: October 2002

Sr2(Ta1-x
,Nb
x
)2O7(STN) ferroelectric thin films have been prepared on SiO2/Si(100) substrates by the pulsed laser deposition (PLD) method. Preferential (110) and (151)-oriented STN thin films were deposited at a low temperature of 600°C in N2O ambient gas at 0.08 Torr. A counterclockwise C–V hysteresis was observed in the metal-ferroelectric-insulator-semiconductor (MFIS) structure using Sr2(Ta0.7,Nb0.3)2O7 on SiO2/Si deposited at 600°C. The memory window in the C–V curve spreads symmetrically towards both positive and negative directions when the applied voltage is increased and the window does not change in sweep rates ranging from 0.1 to 4.0×103 V/s. The C–V curve of the MFIS structure does not degrade after 1010 cycles of polarization reversal. The gate retention time is about 3.0×103 s when the voltage and time of write pulse are ±15 V and 1.0 s, respectively, and the hold bias is -0.5 V.
Time-domain Optimization of the Preparation Condition of Conductive Langmuir-Blodgett Films Based on Ditetradecyldimethylammonium-Au(dmit)2 Salt
Authors: Horikiri Masashi , Miura Yasuhiro F. , Okuma Yoshihito , Ikegami Keiichi , Sugi Michio
Published: October 2002

The conductive Langmuir-Blodgett (LB) film based on ditetradecyldimethylammonium-Au(dmit)2 salt was studied. The film quality at the air/water interface was greatly improved by changing the “waiting time (T
w)”, which is defined as the time between the application of the spreading solution and the onset of compression. The main factor for the morphological improvement is considered to be the oxidation of the Au(dmit)2 moiety at the air/water interface. The resultant conductivity of the LB film was highest in the case of T
w=30 min.
Thin Film Transistor of ZnO Fabricated by Chemical Solution Deposition
Authors: Yutaka Ohya Yutaka Ohya , Tsukasa Niwa Tsukasa Niwa , Takayuki Ban Takayuki Ban , Yasutaka Takahashi Yasutaka Takahashi
Published: October 2002

A ZnO thin film was deposited on a Si wafer having an oxidized SiO2 layer using a chemical solution deposition process and was applied to a bottom-gate type thin film transistor (TFT). The films prepared by combined heating at 600° and 900°C exhibited typical enhancement-type TFT characteristics with electrons as carriers. The low heating temperature around 600°C degraded the insulating properties of the SiO2 layer but high temperature annealing recovered that.
Back-Gated Point Contact
Authors: Hashimoto Katsushi , Miyashita Sen , Saku Tadashi , Hirayama Yoshiro
Published: October 2002

In this study, we fabricated split gates on a back-gated undoped heterostructure to perform transport measurements on a quantum point contact (QPC). Using this back-gated QPC system, we obtained clear quantized conductance plateaus over a wide range of electron densities (1.2×1015 m-2 to 3.3×1015 m-2) without being affected by imperfections. We also observed a clear 0.7 G
0 (G
0=2e
2/h) anomaly. The shape of the anomaly varies with electron density. Furthermore, the conductance value at which this anomaly appears is not precisely 0.7 G
0 but changes with electron density.
Improvement of Growth Process to Achieve High Geometrical Uniformity in InGaAs Ridge Quantum Wires Grown by Selective MBE on Patterned InP Substrate
Authors: Jiang Chao , Muranaka Tsutomu , Hasegawa Hideki
Published: October 2002

Attempts were made to identify and remove the major sources of structural nonuniformity in the InGaAs ridge quantum wires (QWRs) grown by selective molecular beam epitaxy (MBE) on patterned substrates. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and cathodoluminescence (CL) were used to characterize the uniformity of ridge QWR. Nonuniformity of the initial InGaAs ridge structure prior to QWR growth was found to be a key factor to be controlled. Using sufficient pre-growth etching and atomic-hydrogen-assisted cleaning in ultra-high-vacuum (UHV), a defect-free, oxide-free and flat InGaAs/InP interface was realized. By further optimizing the growth parameters using a low V/III beam-equivalent pressure ratio between 30 to 45 at a growth temperature of 500°C, an InGaAs ridge structure with an atomically flat facet having a standard deviation of the ridge top height of 0.25 nm for a 600 nm-long ridge stripe was realized, for the first time. InGaAs QWRs with various effective widths down to 6 nm were grown on this ridge structure, and they exhibited excellent optical properties with enhanced luminescence intensity and narrow linewidth.
Effect of Rapid Thermal Annealing on Oxygen Precipitation Behavior in Silicon Wafers
Authors: Akatsuka Masanori , Okui Masahiko , Morimoto Nobuyuki , Sueoka Koji
Published: October 2002

The effect of rapid thermal annealing (RTA) on oxygen precipitation behavior in Czochralski silicon wafers was investigated with an emphasis on the RTA ambient, temperature and cooling rate. It was found that (i) anomalous oxygen precipitation (AOP) was observed in the case of RTA temperature at ≧1240°C with cooling rates of ≧25°C/s in Ar and in the case of RTA temperature at ≧1200°C with cooling rates of ≧5°C/s in N2, while AOP was not observed in O2, (ii) an M-like depth profile of precipitate density appeared for the cooling rates of ≧50°C/s in Ar, and ≧25°C/s in N2, and (iii) the width of the precipitate denuded zone was larger than the width of outdiffused oxygen in the case of RTA in Ar. The relationships of thermal equilibrium concentrations C
J

* and diffusion constants D
J
were estimated to be C
I
*<C
V
* and D
I>D
V (I: interstitial, V: vacancy) from the experimental results of RTA in Ar and the calculated results using the Voronkov model.
Photo-enhanced Magnetoresistance Effect in GaAs with Nanoscale Magnetic Clusters
Authors: Shon Yoon , Yuldashev Shavkat U. , Fan Xiangjun , Fu Dejun , Kwon Young Hae , Hong Chi Yhou , Kang Tae Won
Published: October 2002

Enhanced positive magnetoresistance effect under light illumination has been observed in GaAs containing nanoscale magnetic clusters. The ferromagnetic clusters were embedded into GaAs by using Mn ion implantation and rapid thermal annealing. Positive magnetoresistance in these structures has been observed and attributed to the scattering of charge carriers by the nanomagnet-dipole field. The enhancement of positive magnetoresistance under light illumination is due to a higher mobility of photoexcited electrons in comparison with the mobility of holes in p-type GaAs prepared by Mn ion implantation.
CO2-Laser-Assisted Plasma-Enhanced Chemical Vapor Deposition of Silicon Dioxide Thin Film
Authors: Tsai Hung-Sheng , Chiu Hsin-Ching , Chang Sheng-Hsiung , Cheng Chao-Chia , Lee Ching-Ting , Liu Hai-Pei
Published: October 2002

The plasma enhanced chemical vapor deposition (PECVD) of silicon dioxide (SiO2) thin films from SiH4 and N2O has been executed with and without CO2 laser illumination. The quality of the film processed under a 10.6 µm CO2 laser was close to that of a film grown when the substrate was heated to 200°C. Since the temperature of the film substrate under CO2 laser illumination was only about 55°C, this method should be helpful in processes where a low thermal budget is required. CO2-laser-assisted PECVD (termed LAPECVD) with a substrate heated to 200°C resulted in a SiO2 thin film with excellent I–V characteristics and surface morphology, as well as a higher refractive index and lower etching rate in BOE solution. Application of this thin film should be explored.
Characterization of Diamond Surface-Channel Metal-Semiconductor Field-Effect Transistor with Device Simulation
Authors: Kazuo Tsugawa Kazuo Tsugawa , Hitoshi Umezawa Hitoshi Umezawa , Hiroshi Kawarada Hiroshi Kawarada
Published: October 2002

The DC operation of surface-channel metal-semiconductor field-effect transistors (MESFETs) using p-type conductive layers on hydrogen-terminated diamond surfaces is investigated by two-dimensional device simulation. As a result, a model to describe the surface semiconducting layer, in which acceptors are distributed two-dimensionally on the surface, is found to reproduce actual device characteristics well. Based on the model, the carrier (hole) concentration at a depth of 10 nm is determined to be three orders less than that at the surface. This thin channel realizes complete channel pinch-off and drain-current saturation with high transconductance, observed in the actual diamond surface-channel MESFETs. In the simulation, the transconductance of diamond surface-channel MESFETs with a self-aligned 1 µm gate exceeds 100 mS/mm. This result agrees well with a recent experimental result. The transconductance over 100 mS/mm can compete with that of Si metal-oxide-semiconductor field-effect transistors (MOSFETs) of the same gate length. The hydrogen-terminated diaomond surface is naturally equipped with the silicon-on-insulator-like (SOI-like) thin channel and shallow junction depth required for a nanoscale FET, such as one with a gate length of less than 50 nm.
Elimination of Dielectric Degradation for Chemical-Mechanical Planarization of Low-k Hydrogen Silisesquioxane
Authors: Chang Ting-Chang , Liu Po-Tsun , Tsai Tsung-Ming , Yeh Fon-Shan , Tseng Tseung-Yuen , Tsai Ming-Shih , Chen Ben-Chang , Yang Ya-Liang , Sze Simon-M.
Published: October 2002

The characteristics of post-chemical mechanical polishing (post-CMP) low-k hydrogen silsesquioxane (HSQ) have been investigated in this work. Dielectric properties of HSQ are damaged by the CMP process. We propose NH3-plasma treatment to improve the characteristics of post-CMP HSQ film. Both of the leakage current and dielectric constant of NH3 plasma-treated HSQ are significantly decreased as compared with those of untreated HSQ. NH3 plasma treatment slightly nitridates the surfaces of the polished HSQ film. The thin nitride layer prevents moisture absorption in the post-CMP HSQ. As a result, the dielectric degradation of HSQ after the CMP process can be effectively recovered using the NH3 plasma treatment.
Formation of TiO2 Thin Films using NH3 as Catalyst by Metalorganic Chemical Vapor Deposition
Authors: Jung Sung-Hoon , Kang Sang-Won
Published: October 2002

We have studied metalorganic chemical vapor deposition of TiO2 thin films using titanium tetra-isopropoxide [TTIP, Ti(O–C3H7)4] and NH3 as a catalyst at deposition temperatures ranging from 250 to 365°C. At deposition temperatures above 330°C, pyrolytic self-decomposition of TTIP is dominant regardless of the use of NH3, and the activation energy for TiO2 film formation is 152 kJ/mol. At deposition temperatures below 330°C, the films can be formed with the help of the catalytic activity of NH3, and the activation energy is reduced to 55 kJ/mol. TiO2 films deposited through the pyrolytic self-decomposition of TTIP have an anatase structure before and after performing post-deposition annealing in oxygen ambient for 30 min at 750°C. On the other hand, the as-deposited films formed through the catalytic reaction of TTIP with NH3 incorporate nitrogen impurities and have microcrystallites of the rutile structure within the amorphous matrix. However, the post-deposition annealing, the nitrogen impurities are completely removed from the films, and the films are converted into polycrystalline TiO2 films with the rutile structure, which have a high dielectric constant of 82 and a low leakage current.
Far-Infrared Reflectance and Transmittance Studies of YBa2Cu3O7-x Single-Crystal Thin Films
Authors: Shibata Hajime , Kimura Shinji , Kashiwaya Satoshi , Ueno Shigehiro , Koyanagi Masao , Terada Norio , Kawate Etsuo , Tanaka Yukio
Published: October 2002

A new method of estimating the optical constants of thin films has been developed and applied to YBa2Cu3O7-x
epitaxial single-crystal thin films (T
c=90 K) grown on MgO substrates to determine the far-infrared optical conductivity σ
ab
(ω), which is the response when an unpolarized excitation is applied parallel to the ab-plane in multidomain (twinned) single crystals of YBa2Cu3O7-x
. In this method, both the transmittance spectra T(ω) and reflectance spectra R(ω) are measured as a function of the wave number ω, and the results are substituted into a set of coupled equations which exactly describe R(ω) and T(ω) of thin films on substrates, where the complex refractive index N=n+i
k of the thin films is an unknown parameter. The coupled equations are numerically solved using the Newton method, and the values of n and k are determined as a function of ω. We have determined σ
ab
(ω) of YBa2Cu3O7-x
thin films for ω=50–250 cm-1 at T=34–97 K. Analysis of the temperature dependence of σ
ab
(ω) based on the two-fluid model suggests that the symmetry of the superconducting pairing state of the specimen is d-wave.
Polycrystalline Ni Ferrite Films Deposited by RF Sputtering Techniques
Authors: Samarasekara P. , Cadieu F. J.
Published: October 2002

Properties of sputtered polycrystalline Ni ferrite (NiO: Fe2O3) films were studied in detail. All these films were sputtered on Al2O3 polycrystalline substrates. The coercivity of the films drastically increased from 5 to 800 Oe as the deposition temperature was raised from 60 to 600°C. Polycrystalline ferrite films with higher coercivity are useful for high-density recording media. It is difficult to directly or subsequently (with annealing) deposit aligned (or oriented) films of Ni ferrite on polycrystalline substrates according to our studies. The X-ray diffraction patterns, scanning electron microscope (SEM) measurements and magnetic measurements were performed for these Ni ferrite films.
Gain and Spectral Characteristics of Broadband Optical Parametric Amplification
Authors: Zhang Shu-Kui , Fujita Masayuki , Yoshida Hidetugu , Kodama Ryousuke , Yamanaka Masanobu , Izawa Yasukazu , Yamanaka Chiyoe
Published: October 2002

Investigations on broadband optical parametric amplification (OPA) are presented. Weak chirped-pulses are effectively amplified to milli-Joule level in short nonlinear crystals when pumped by frequency-doubled YAG lasers. The gain and spectral characteristics of chirped-pulse signals under different pumping conditions are analyzed.
GaN-Based High Power Blue-Violet Laser Diodes
Authors: Tojyo Tsuyoshi , Asano Takeharu , Takeya Motonobu , Hino Tomonori , Kijima Satoru , Goto Shu , Uchida Shiro , Ikeda Masao
Published: October 2002

The epitaxial lateral overgrowth (ELO) technique is an important technology for improving the characteristics of GaN-based laser diodes (LDs). The photoluminescence intensities from GaN and GaInN multiple quantum well active layers in the ELO-GaN wing region were found to be higher than those in the seed region. This indicates that the density of dislocations in the wing region could be reduced significantly. This is evidenced by dislocation densities of less than 106 cm-2 as determined from transmission emission microscopy and etching-pit-density measurements. The cleaved facets of LDs on ELO-GaN and sapphire were observed by atomic forced microscopy. Although the roughness of GaN cleaved facets on sapphire were high (Ra>10 nm), the roughness in the ELO-GaN wing region was found to be as smooth as that of GaAs cleaved facet (Ra<1 nm). The characteristics of LDs on ELO-GaN were found to be superior to those on sapphire as a result of smoother facets and lower dislocation densities.
Study of Overwrite Jitter in Phase Change Optical Recording at High Velocities
Authors: Sheila Aparna C. , Schlesinger T. E.
Published: October 2002

In this paper, we simulate overwrite in a phase change recording disk and study the overwrite characteristics at high velocities (data rates). An absorption controlled disk is used and overwrite jitter is seen to increase with velocity. A modified multipulse scheme with a lower power in the first pulse of the multipulse is proposed for high velocities and it is shown that using this, the overwrite jitter can be reduced.
Electronic Structure Analyses of Sn-doped In2O3
Authors: Hidefumi Odaka Hidefumi Odaka , Yuzo Shigesato Yuzo Shigesato , Takashi Murakami Takashi Murakami , Shuichi Iwata Shuichi Iwata
Published: October 2002

Electronic structures of Sn-doped In2O3(ITO) have been investigated for the first time by using a first-principles calculation method based on the density functional theory. Calculated partial density of states (PDOS) analyses showed that a Sn atom substituted for an indium one formed three impurity bands with s-like symmetry, the second band of the three bands overlapped the conduction band of In2O3, and the Fermi energy of ITO was captured in this impurity band. The PDOS analyses also revealed that the substitution of a Sn atom did not significantly destroy the shape of density of states around the bottom of the conduction band, which gave a physical foundation for the Burstein-Möss shift model used up to now. Carrier generation mechanism and past experimental results, such as those of X-ray photoelectron spectroscopy, temperature dependency of electrical conductivity and carrier-concentration dependency of optical effective mass of ITO, are discussed based on the present theoretical calculation results.
A Method of Generating Full Color in a Liquid Crystal Display Using Birefringent Filters
Authors: Saeed Salman , Bos Philip J. , Li Zili
Published: October 2002

Color generation in a typical liquid crystal device (LCD) is usually done via an array of absorptive color filters placed over the LC subpixels. These filters offer at best 33% transmission resulting in dark displays and the need for high intensity backlights. In this paper we clearly explain a new method of color generation based on a polarization interference filter (PIF) scheme called the Solc filter. The design offers high throughput and chromaticity due to its non-absorptive nature. The design is based on work done by ColorLink Inc. and is extended to show possible use in a display device.
Analysis of Totally Reflected Light from Liquid Crystal Cell using Renormalized Ellipsometry
Authors: Satoshi Okutani Satoshi Okutani , Munehiro Kimura Munehiro Kimura , Hirokazu Toriumi Hirokazu Toriumi , Ken-ichi Akao Ken-ichi Akao , Toshiyasu Tadokoro Toshiyasu Tadokoro , Tadashi Akahane Tadashi Akahane
Published: October 2002

Standard ellipsometry is usually applied for the evaluation of an optical isotropic system, but it is insufficient to analyze light reflected from an anisotropic system such as a liquid crystal (LC) cell. In order to analyze the light reflected from the LC cell, the standard ellipsometry system combined with the photo elastic modulator was extended to renormalized ellipsometry by introducing the definition of the renormalized reflection coefficients without any modification of the conventional experimental procedure. The experimental results such as the ellipsometric angles versus the rotation angle of the LC cell and the dependence of the ellipsometric angles on the applied electric field were in good agreement with the theoretical results based on renormalized ellipsometry. From these results, it was confirmed that renormalized ellipsometry was quite a useful technique to analyze the totally reflected light from the LC cell.
Surface Morphological Structures of 4H-, 6H- and 15R-SiC (0001) Epitaxial Layers Grown by Chemical Vapor Deposition
Authors: Kimoto Tsunenobu , Chen Zhi Ying , Tamura Satoshi , Nakamura Shun-ichi , Onojima Norio , Matsunami Hiroyuki
Published: October 2002

Surface structures of SiC epitaxial layers grown on 4H-, 6H- and 15R-SiC (0001) substrates have been investigated using an optical microscope and an atomic force microscope (AFM). SiC epitaxial layers of 5–15 µm thickness have been grown by chemical vapor deposition on 4H-, 6H- and 15R-SiC (0001) Si-face substrates with 0.2–8.0° off-angle. AFM observation reveals that macrostep formation with a submicron periodicity is reduced by increasing the off-angle of substrates, leading to a small surface roughness of 0.18–0.22 nm. The bunched steps with two and three Si–C bilayer heights are dominant for 4H- and 6H-SiC epitaxial layers, respectively, while 15R-SiC epitaxial layers show both two and three Si–C bilayer height steps, reflecting the peculiar stacking structure of each polytype. By optimization of the growth process, the surface defect density has been reduced from 1200–4500 cm-2 to 50–250 cm-2.
Limitation of Nitrogen Incorporation into the Hydrogenated Amorphous Carbon Nitride Films Formed from the Dissociative Excitation Reaction of CH3CN
Authors: Haruhiko Ito Haruhiko Ito , Noriko Ito Noriko Ito , Tsutomu Takahashi Tsutomu Takahashi , Daisuke Tanaka Daisuke Tanaka , Hirosuke Takamatsu Hirosuke Takamatsu , Hidetoshi Saitoh Hidetoshi Saitoh
Published: October 2002

High-resolution CN(B2Σ+–X2Σ+) and CH(A2Δ–X2Π) emission spectra were observed for the dissociative excitation reaction of CH3CN with the microwave-discharge flow of Ar for synthesizing hydrogenated amorphous carbon nitride (a-CN
x
:H) films. The simulation analysis of these spectra revealed that the relative number density of CH(A) to that of CN(B), N
CH(A)/N
CN(B), was strongly dependent on the pressure of Ar, P
Ar, in the range of P
Ar=0.1–0.8 Torr. The P
Ar-dependence of N
CH(A)/N
CN(B) showed a strongly negative correlation with that of the [N]/([N]+[C]) ratio obtained in our previous structural analysis of the films [Saitoh et al.: Jpn. J. Appl. Phys. 39 (2000) 1258]. This correlation was fully explained in terms of the consumption of the CN radical by the hydrogen-abstraction reaction from the film surface, preventing the incorporation of the nitrogen atoms into the a-CN
x
:H films.