Ultrahigh-quality single crystals of silicon carbide by alternate repetition of growth perpendicular to c-axis

The dislocation structure of grown crystals perpendicular to c-axis was investigated by means of X-ray analysis. It was revealed that the dislocations were almost straight parallel to the growth direction in the crystals. The alternate repetition of growth in the direction to and made the dislocations and lattice distortion successfully reduced. The mechanism for the reduction was attributed to less exposure of the dislocations to a seed surface, because the straight dislocations in the seed crystal exist parallel to the seed surface. A crystal grown on {0 0 0 1} seed substrate sliced out from the crystal by the alternate repetition of growth had drastically lower defect density than conventional crystals.     

A 1-V RF-CMOS LNA design utilizing the technique of capacitive feedback matching network

In this paper, a CMOS low-noise amplifier (LNA) with a new input matching topology has been proposed, analyzed and measured. The input matching network is designed through the technique of capacitive feedback matching network. The proposed LNA which is implemented in a technology is operated at the frequency of 12.8 GHz. It has a gain S21 of 13.2 dB, a noise figure (NF) of 4.57 dB and an NF_min of 4.46 dB. The reverse isolation S12 of the LNA can achieve and the input and output return losses are better than . The input 1-dB compression point is and IIP3 is . This LNA drains 10 mA from the supply voltage of 1 V.     

A CMOS image sensor with light-controlled oscillating pixels for an investigative optobionic retinal prosthesis system

This paper presents a high-dynamic range CMOS image sensor architecture incorporating light-controlled oscillating pixels which can act as front-end for an investigative optobionic retinal prosthesis research effort. Each pixel acts as an independent oscillator, whose frequency is proportional to the local light intensity. A 9×9 pixel array has been fabricated in the AMS CMOS opto process. Each pixel's area amounts to , each pixel photodiode area is while the array occupies . Measured results show that the sensor can achieve a linear optical dynamic range of 80 dB (from 0.24 Hz to 2.2 kHz). Its linear electrical dynamic range exceeds 134 dB (from 100 mHz to 502 kHz). The nominal power dissipation is about 50 nW per pixel.     

High-mobility pentacene thin-film transistors with copolymer-gate dielectric

Pentacene thin-film transistors have been obtained using polymethyl-methacrylate-co-glyciclyl-methacrylate (PMMA-GMA) as the gate dielectric. The optimum active layer thickness in thin-film transistors (OTFTs) was investigated. The present devices show a wide operation voltage range. The on/off current ratio is as high as 10⁵. In linear region (), the field-effect mobility of device increases with the increase in gate field at low-voltage region (), and a mobility of 0.33 cm²/V s can be obtained when . In saturation region, the mobility increases linearly with the gate field, and a high mobility of 1.14 cm²/V s can be obtained at . The influence of voltage on mobility of device was investigated.     

Ionic outgassing from photoacid generators upon irradiation at 13.5 nm

Photoresist outgassing is considered a possible source of contamination of optics in extreme ultraviolet (EUV) lithography at 13.5 nm. We measured the relative proportions of ionic outgassing from 18 commercially available photoacid generators (PAG), which is a key component of chemically amplified photoresists, upon irradiation at 13.5 nm. These PAG include 17 triarylsulfonium or diaryliodonium salts, which contain or as the anion, and one PAG of molecular type. The overall outgassed ions in the range 10-200 u were counted in relative proportions. Outgassing of F⁺ is found to be dominant, and for most PAG the extent of F⁺ outgassing shows a satisfactory correlation with the ratio of F atomic photoabsorption to the overall PAG photoabsorption. Outgassed ions F⁺, CF⁺, and from PAG containing the anion and additional such as , and from those containing are identified. Triphenylsulfonium perfluoro-1-butanesulfonate is one PAG to emit the most abundant F⁺ and total ionic fragments, and a PAG of molecular type (N-hydroxy-5-norbornene-2,3-dicarboximide perfluoro-1-butanesulfonate) also emits abundantly both hydrocarbon ions and F⁺. Ionic outgassing of PAG cations includes (C₆H₅)₂S⁺ from R(C₆H₅)₂S⁺ salts and I⁺ from diaryliodonium salts. For PAG containing t-C₄H₉, significantly less F⁺ outgassing is observed; additional outgassing pathways are proposed. The pressure rise caused by PAG shows no dependence on the anion identity, but is correlated with cation photoabsorption, and ascribed to neutral aryl outgassing. Other minor outgassing species include from sulfonates; and ‘photostable’ PAH cations are identified for the first time and provide evidence of concurrent outgassing from, and polymerization of, PAG upon irradiation at 13.5 nm.     

Low-voltage nanopower clock generator for RFID applications

The design of an on-chip RC-based oscillator, implemented in a standard BiCMOS process, without any external component, is presented. The proposed oscillator provides a clock signal at a frequency of 50 kHz with a temperature coefficient smaller than 0.3%/^°C over a temperature range from 0 to , without any external trimming. The proposed oscillator operates with a supply voltage of 0.8 V and has a power consumption of at room temperature. The chip area is .     

High-speed CMOS unity-gain current amplifier

A high-performance CMOS unity-gain current amplifier is proposed. The solution adopts two feedback loops to reduce the input resistance and a nested-Miller technique to provide frequency compensation. A design example using a 0.8 μm process and a 2 V supply is given and SPICE simulations show a bandwidth of 75 MHz, no slew-rate limitations and a settling time better than 50 ns, irrespective of the current amplitude. Input and output resistances are better than 0.1 Ω and 15 MΩ, respectively. The input-referred white noise spectral density is .     

Occurrence of ferroelectricity in epitaxial BiMnO3 thin films

In this paper, we report evidence of ferroelectricity in perovskite manganite (BiMnO₃) thin films synthesized via r.f. magnetron sputtering method on a single-crystal (1 0 0)-oriented SrTiO₃:Nb 0.1% and Pt/TiO₂/SiO₂/Si substrates. X-ray diffraction measurements were used to analyse the crystal structure of the thin films, revealing epitaxial growth for BiMnO₃ films with their (1 1 1) and (2 2 2) planes parallel to the (0 0 1) and (0 0 2) planes of the SrTiO₃ substrate. AFM measurements were performed to investigate surface morphology; quantitative values of roughness and grain size are in the range between 300 and 500 nm. Ferroelectric characterization was conducted at low temperatures and at 300 K. Hysteresis loops (polarization vs. voltage) were obtained, showing saturation polarizations of , and at 105, 122, and 300 K. Resistance vs. temperature measurements were performed, which indicated this to be very robust insulating material.     

A high precision low dropout regulator with nested feedback loops

A high precision low dropout regulator (LDO) with nested feedback loops is proposed in this paper. By nesting a zero-tracking compensation loop inside of the negative feedback loop comprising an error amplifier, the independence of off-chip capacitor and effective series resistance (ESR) is ensured for different load currents and operating voltages. This circuit is designed and fabricated using a standard CMOS process. The die area is a . The measurement results show that the total error of the output voltage caused by line and load variations is less than ±3% in low quiescent current (Iddq) or low voltage scenarios. Besides, the smallest dropout of the LDO, 0.11 V, while the output current is 165 mA, the output load is and 20 in parallel.     

An ultra-low power integer-N frequency synthesizer for MICS transceivers

The ultra-low power frequency synthesizer for the transceivers used in the application of Medical Implantable Communication Services (MICS) is presented. The MICS band is from 402 to 405 MHz. Each channel spacing is 300 kHz. Integer-N architecture is used to implement the frequency synthesizer. The post layout simulations show that the total power consumption of the system is less than at 1.2 V power supply. The gains of the charge pump and voltage controlled oscillator (VCO) are and 50 MHz/V, respectively. The standard 300 kHz external clock is used as the reference. The design is carried out in the IBM 90 nm 9LPRF CMOS technology.     

PAMBE growth of (1 1 2¯ 2)-oriented GaN/AlN nanostructures on m-sapphire

We report on the plasma-assisted molecular-beam epitaxial growth of (1 1 2¯ 2)-oriented GaN/AlN nanostructures on (1 1¯ 0 0) m-plane sapphire. Moderate N-rich conditions enable to synthesize AlN(1 1  2) directly on m-sapphire, with in-plane epitaxial relationships [1 1 2¯ 3¯]_AlN∥[0 0 0 1]_sapphire and [1  0 0]_AlN∥[1 1 2¯ 0]_sapphire. In the case of GaN, a Ga-excess of one monolayer is necessary to achieve two-dimensional growth of GaN(1 1 2¯ 2). Applying these growth conditions, we demonstrate the synthesis of (1 1 2¯ 2)-oriented GaN/AlN quantum well structures, showing a strong reduction of the internal electric field. By interrupting the growth under vacuum after the deposition of few monolayers of GaN under slightly Ga-rich conditions, we also demonstrate the feasibility of quantum dot structures with this orientation.     

Self-aligned In0.49Ga0.51P/GaAs HBT DC and RF characteristics related with orientations

A self-aligned InGaP/GaAs HBT DC and RF characteristics related with orientations were studied. The DC current gain was greater for the [0 1 1] emitter orientation compared to orientation. However, it also showed slightly better RF performance for orientation with a cutoff frequency f_T 69 GHz compared to the f_T of 62 GHz for the [0 1 1] orientation. This experimental work has been proposed that the dependence of the characteristics could be attributed to both piezoelectric effect and the difference between lateral etched profiles in different directions.     

Porous silicon thin film as CO sensor

This work presents the electric behavior of porous silicon (PS) thin films when the material's surface is exposed to carbon monoxide. PS thin films were fabricated by the electrochemical anodization method of Si-c (1 0 0) substrates with resistivity . The samples were prepared at 20 min anodization time and anodization current. Aluminum electrodes were deposited on the surface of the material by high vacuum evaporation, such that the electric conduction was parallel to the substrate's surface. The detector was placed in vacuum during 1 h and then CO was allowed into the vacuum chamber. Measurements of the I-V characteristic were carried out at atmospheric pressure, in vacuum and with CO. Changes in the resistance of the material, of about MΩ, were observed in the different samples, indicating that the material is sensitive to the presence of CO and therefore suitable as gas sensor.