Special Issue: Integrated Circuits Design

Guest Editor: Michal Horak

Title of the Paper: Snap-back characteristics tuning of SCR-based semiconductor structures

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Authors: Petr Běťák, Vladislav Musil

Abstract: Semiconductor structures having snap-back type of I-V characteristics are very useful in ESD (electrostatic discharge) protection design. ESD protection structures act as a protection of integrated circuits against the parasitic electrostatic discharge. The typical protection structure having the snap-back type of I-V characteristic is a SCR (silicon controlled rectifier) or a gate grounded NMOS transistor. This text is dealing with structures which enable tuning of I-V snapback characteristics. The simulated technology was CMOS very high voltage (VHVIC). The measurement was done for samples manufactured in 1.5μm BiCMOS.

Keywords: SCR, snap-back, ESD

Title of the Paper: New mixing rule of polymer composite systems

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Authors: Holcman Vladimír, Liedermann Karel

Abstract: The paper studies dielectric properties of elastomer filled with Ni spherical particles of different sizes within the range 35 – 115 μm. The experimental analysis is followed by the examination permittivity/conductivity mixing rules. A new mixing formula for the composite system consisting of spherical metallic particles and polymer matrix is presented. This formula includes both Ni particle content and Ni particle size as two independent variables

Keywords: composites, polymer, permittivity, mixing rule, rules of mixture, measurement

Title of the Paper: Microplasma Noise as a Tool for PN Junctions Diagnostics

Authors: P. Koktavy, R. Macku, P. Paracka, O. Krcal

Abstract: The present paper deals with noise diagnostics of PN junctions in semiconductor devices. The general tool to be employed here is the microplasma noise, which arises in reverse biased PN junctions containing local defects featuring lower breakdown voltage than the rest PN junction. When a high electric field is applied to this PN junction, local breakdowns arises in micro-sized regions, which in turn can lead to the deterioration in quality or destruction of the PN junction. It is therefore advisable to use methods which can indicate the presence of these regions in the junction and make the quality assessment and quantitative description of the tested devices possible.

Keywords: Noise diagnostics, quality, PN junction, microplasma, avalanche breakdown, impact ionization

Title of the Paper: Advanced non-destructive diagnostics of monocrystalline silicon solar cells

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Authors: R. Macku, P. Koktavy, P. Skarvada

Abstract: Measurements of reverse-biased junctions can provide valuable information on the solar cells and their defects. A number of papers were published in the past concerning the measurement methodology, however, for devices having relatively low pn junction area only. The junction area is much larger in solar cells. Therefore, a new measurement methodology had to be developed for them. In large-area pn junctions, there are some phenomena which are negligible in the smaller-area junction measurements, but are introducing considerable errors in the measurement results of large-area junctions. The barrier capacity is one of the parameters of the solar cells under investigation. We employed the near-field and the electron microscopy to study the solar cell surface texture, which provided us with some information on the pn junction configuration.

Keywords: solar cell, pn junction, barrier capacitance, scanning near-field optical microscopy (SNOM)

Title of the Paper: Noise Spectroscopy of GaN/AlGaN HFETs

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Authors: Jan Pavelka, Nobuhisa Tanuma, Munecazu Tacano, Josef Sikula

Abstract: Noise characteristics of epitaxial n-GaN on sapphire layers and GaN/AlGaN on sapphire or SiC HFET structures were investigated in the temperature range from 13K to 300K. Ohmic contacts were made using Ti/Al/Ni/Au and contact noise was found negligible by TLM analysis. The Hooge parameter αH of epitaxial GaN was 2×10^-3 at 300K, gradually decreasing to 10^-4 around 50K. For GaN/AlGaN on sapphire HFET the g-r noise was dominant at almost every temperature, allowing only to determine αH = 2×10^-4 at 22K. The GaN/AlGaN on SiC HFETs were characterized by αH values of 10^-4 to 10^-5.

Keywords: GaN, GaN/AlGaN, HFET, HEMT, 1/f noise, g-r noise, Hooge parameter

Title of the Paper: Application of Microplasma Noise Statistical Characteristics to Studying the PN Junction Heating in the Neighbourhood of Local Defects

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Authors: M. Raska, P. Koktavy

Abstract: Local avalanche breakdowns take place in the neighbourhood of PN junction local defects at sufficiently high reverse voltage. These breakdowns give rise to microplasma noise which is often characterized by current impulses whose inception time and duration time are random. The effective crosssection of the microplasma region being rather small, the current density may achieve a high value, which in turn can result in local heating of the micro-region and, consequently, the junction destruction. The present paper deals with the effect of the temperature on statistical characterics of microplasma noise. This effect is intended to be used for the local defect temperature determination based on these characteristic measurement results.

Keywords: Microplasma noise, PN junction, Avalanche breakdown, Statistical characteristic, Noise diagnostics

Title of the Paper: Constitutive Relations and Conditions for Reciprocity in Bianisotropic Media (Macroscopic Approach)

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Authors: M. Strunc

Abstract: The paper deals with reciprocity relations in bianisotropic electromagnetic materials. Different forms of material constitutive relations are discussed and reciprocity conditions for different approaches to their derivation are considered.

Keywords: Reciprocity principle, bianisotropic electromagnetic media, constitutive relations, reciprocal materials

Title of the Paper: Reciprocity Principle in Bianisotropic Composite Media (Microscopic Approach)

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Authors: M. Strunc

Abstract: The paper deals with reciprocity relations in bianisotropic electromagnetic materials. Conditions for reciprocity are expressed and discussed in connection with macroscopic and microscopic level of consideration and with space-time symmetry properties of media. Newly is the connection between microscopic and macroscopic treatment to reciprocity theorem analyzed namely with respect to composed bianisotropic media.

Keywords: Microscopic reciprocity, bianisotropic media, space-time reversal symmetry, composite media

Title of the Paper: Projection of Solar Cell Back Side Contact to the LBIC Image

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Authors: Vanek J., Jandova K., Barinka R.

Abstract: This work presents a detailed analysis of the LBIC images with visible back side contact. The LBIC measurement for a solar cell local characterization has been developed and tested on mono-crystalline silicon solar cells. The solar cells were locally illuminated by a focused light source of different wavelengths. The response (current or potential) of the solar cell was measured at stationary conditions during the scanning process. A large number of independent data with high spatial resolution were obtained. Applying an advanced fitting procedure on these data yields a set of local parameters for each point on the solar cell, giving information on the distribution of the photo current, series, shunt resistance and lateral diffusion of minority carriers. The theoretical approach to this technique will be discussed and the applicability of this characterization tool will be demonstrated and compared. We have studied a group of silicon solar cells with good and wrong standard parameters. In this part we describe our study of the comparison between LBIC images with different wavelengths of the light source and explain the projection of back side contact of LBIC image by the theory of secondary emission of infrared light.

Keywords: LBIC, wavelength, silicon solar cell, back side contacts, front side contacts, luminescence

Title of the Paper: RTS Noise in Si MOSFETs and GaN/AlGaN HFETs

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Authors: Jan Pavelka, Josef Šikula, Munecazu Tacano

Abstract: Low frequency noise of Si n-MOSFET and GaN/AlGaN HFET devices was measured in 10 μHz to 100 kHz range, given by 1/f noise and RTS noise components. RTS noise voltage signal was analysed by means of zero cross method in 1 ms to 100 s windows and noise spectral density of crossing events was found almost constant in the 10-5 to 103 Hz frequency range in all samples. This indicates that there is no 1/f fluctuation of crossing rate given by trap characteristics, although charge carrier transport mechanisms give rise to quite different 1/f noise levels in Si and GaN devices. Statistical analysis of carrier capture and emission events duration revealed departure from exponential distribution in some samples, but any correlation among successive pulses wasn’t obvious.

Keywords: GaN, GaN/AlGaN, HFET, MOSFET, 1/f noise, RTS noise