A System for Logical Design of Custom CMOS VLSI Functional Blocks with Reduced Power Consumption

We describe a CMOSLD system to automate the design of irregular logic circuits of CMOS library elements. The main criteria of circuits optimization are the area and the power consumption. This system is integrated with software packages Questa Sim, LeonardoSpectrum, and Accusim II (Mentor Graphics). This makes it possible to perform efficiently logical simulation, synthesis, resynthesis and estimation of energy consumption based on logical and circuit simulation.     

Analog/RF Study of Self-aligned In<Subscript>0.53</Subscript>Ga<Subscript>0.47</Subscript>As MOSFET with Scaled Gate Length

This study presents the impact of gate length scaling on analog and radio frequency (RF) performance of a self- aligned multi-gate n-type In_0.53Ga_0.47As metal oxide semiconductor field effect transistor. The device is fabricated using a self-aligned method, air-bridge technology, and 8 nm thickness of the Al₂O₃ oxide layer with different gate lengths. The transconductance-to-normalized drain current ratio (g _m/I _D) method is implemented to investigate analog parameters. Moreover, g _m and drain conductance (g _D) as key parameters in analog performance of the device are evaluated with g _m/I _D and gate length variation, where g _m and g _D are both showing enhancement due to scaling of the gate length. Early voltage (V _EA) and intrinsic voltage gain (A _V) value presents a decreasing trend by shrinking the gate length. In addition, the results of RF measurement for cut-off and maximum oscillation frequency for devices with different gate lengths are compared.     

Two-electron tin centers formed in lead chalcogenides as a result of nuclear transmutations

It is shown that the emission [^119mmSn(^119mSn)] and absorption (¹¹⁹Sn) Mössbauer spectra of impurity tin atoms in lead chalcogenides are identical. It is assumed that the mechanism of emergence of multi-charged tin ions as a result of conversion isomeric transition in the parent ^119mmSn atom is valid only for free atoms, whereas the final charge state of a stabilized daughter atom in condensed media with a high concentration of charge carriers is the charge state of the parent atom. The large value of recoil energy for ¹¹⁹Sb atoms after radioactive decay of parent ^119mTe atoms gives rise to a significant number of displaced ^119mSn atoms; however, a greater fraction of ^119mSn atoms after the ^119mTe → ¹¹⁹Sb → ^119mSn decay remains in the anionic sublattice and are antisite defects. In contrast to tin atoms in the cationic sublattice, the ^119mSn antisite defects are found to be electrically inactive centers.     

Analysis and Simulation of Vertical Complementary Silicon Bipolar Transistors

The features of modern complementary bipolar technologies (CB-technologies) for analog applications have been analyzed and the main trends in their development are considered. Different industrial CBtechnologies are compared on the basis of two parameters of complementarity, namely the quality factor (βV _A ) and Johnson’s parameter (BV _CEO f _T ). The p-epitaxial-planar CB-technology has been studied by the method of two-dimensional numerical simulation using the TCAD Sentaurus software for vertical n–p–n and p–n–p transistors. A careful calibration of the parameters of technological and electrophysical 2D models on the basis of test structures has shown sufficient accuracy of the used methodology for practice.     

Efficient Techniques for Fault Detection and Correction of Reversible Circuits

It is very important to detect and correct faults for ensuring the validity and reliability of reversible circuits. Test vectors play an important role to detect as well as correct the faults in the circuits. The optimum number of test vector implies the more capabilities for detecting several types of faults in the circuits. In this paper, we have proposed an algorithm for generating optimum test vectors. We have shown that the proposed algorithm generates optimum test vectors with the least complexity of time as compared to existing methods, i.e., we have proved that the proposed algorithm requires O(log ₂ N) time, whereas the best known existing method requires O(N. log ₂ N) time, where N is the number of inputs. We have also proposed another algorithm for detecting faults using the generated test vectors. This proposed method can detect more faults than existing ones. We have proved that the proposed fault detection algorithm requires least time complexity as compared to the best known existing methods, i.e., the proposed algorithm requires O(d. 1/N) time, whereas the best known existing methods require O(d. N) time, where N is the number of inputs and d is the number of gates in a reversible circuit. Finally, we have proposed another algorithm for correcting the detected faults. We have also proved that the proposed methods require the least time complexity as compared to the best known existing methods. In addition, the experimental results using benchmark circuits show the efficiency of the proposed methods.     

Diamond Diode Structures Based on Homoepitaxial Films

(m–i–p)-Structures with high-resistance epitaxial i-layers are fabricated on heavily doped p⁺-type substrates with platinum contacts. The structures are studied using several methods: optical and electron microscopy and luminescence, and electrophysical (C–V and I–V characteristics) methods and tested as detectors of ionizing radiation. It is shown that the (m–i–p)-structures are promising for development of several electronic devices (high-voltage diodes, detectors of ionizing radiation, and photovoltaic devices).     

Photoconductivity of the Pb<Subscript>0.75</Subscript>Sn<Subscript>0.25</Subscript>Te:In alloy in an alternating electric field

Kinetics of variations in the components of total impedance for single-crystal Pb_0.75Sn_0.25Te:In samples is investigated upon switching on and switching off of the illumination source at temperature 4.2 K and frequency 10⁶ Hz. The calculation carried out in the context of representation of equivalent circuits showed that the parameters of a parallel R _p C _p chain, which approximates the sample behavior, correlate strictly. In the region of low resistances R _p , the values of C _p increase abruptly following the law C _p ∝ R _p ^?2 . It is of no importance what method of decreasing the resistance is used—heating of the sample or its illumination at low temperature. The obtained results were analyzed taking into account the contribution of the impurity subsystem to conductivity and the possible manifestation of Maxwell-Wagner-type effects.     

New CMOS process using a thermal-oxide mask for making <Emphasis Type="Italic">n</Emphasis><Superscript>−</Superscript>- and <Emphasis Type="Italic">p</Emphasis><Superscript>−</Superscript>-Wells

A new manufacturing process is proposed and evaluated for CMOS memory circuits that is designed to decrease labor input and to increase yield. It essentially uses thermal silicon dioxide instead of silicon nitride as the material of the mask for n ^?- and p ^?-wells, and employs an improved doping procedure for the wells. The new process is shown to decrease considerably the residual stress and defect density in the wafer. Its advantages over the standard process are supported by a two-dimensional computer simulation with Silvaco’s SSUPREM4.     

On <Emphasis Type="Italic">g</Emphasis><Subscript>m</Subscript>-boosted follower-amplifier and its novel circuit transformation based mid-band derivations

This brief paper investigates the small-signal mid-band behavior of g _m-boosted follower-amplifiers which has not been explored previously and whose analysis is not available in text-books or any other source. Both g _m-boosted source follower and g _m-boosted emitter follower are considered in the mid-band analysis. A novel circuit/source transformation based “pictorial” technique with progressively simplified circuit diagrams is employed for this mid-band analysis which generally eliminates the need for solving nodal or mesh equations. Final expression is often achieved by inspection of the simplified circuit without the need for circuit analysis. The paper also discusses g _m-boosted BiCMOS follower amplifier using substrate PNP device in a pure CMOS process. The analysis demonstrates that the unity gain accuracy of follower-amplifier can be considerably enhanced using the g _m-boosting technique without sacrificing bandwidth.     

Special features of the Fourier spectra of magnetoresistance oscillations in a heavily doped heterostructure

The Fourier spectra of oscillations of magnetoresistance in the heavily doped Al _x Ga_{1 ? x} As:Si/GaAs heterostructure, with filling of the two size-quantization subbands, the ground subband E _m and the excited subband E _p , are studied. In the concept of the probabilities of intrasubband and intersubband transitions involving the Landau levels, the origin of harmonics at the frequencies F _m ± F _p in the oscillations of magnetoresistance are interpreted. The ratio between the peak amplitudes A _m and A _p at the frequencies F _m and F _p of the harmonics is close to unity, with equal probabilities of the relations A _m /A _p > 1 and A _m /A _p < 1. At A _m /A _p > 1, the damping of the Landau quantization is controlled by the Coulomb potential, whereas at A _m /A _p < 1 it is controlled by relaxation of two-dimensional electrons due to the heterointerfacial roughness.     

Electronic Processes in CdIn<Subscript>2</Subscript>Te<Subscript>4</Subscript> Crystals

The results of investigations of electrical, optical, and photoelectric properties of CdIn₂Te⁴ crystals, which were grown by the Bridgman method are presented. It is shown that electrical conductivity is determined mainly by electrons with the effective mass m_n = 0.44m₀ and the mobility 120–140 cm²/(V s), which weakly depends on temperature. CdIn₂Te₄ behaves as a partially compensated semiconductor with the donor-center ionization energy E_d = 0.38 eV and the compensation level K = N_a/N_d = 0.36. The absorption-coefficient spectra at the energy hν < E_g = 1.27 eV are subject to the Urbach rule with a typical energy of 18–25 meV. The photoconductivity depends on the sample thickness. The diffusion length, the charge-carrier lifetime, and the surface-recombination rate are determined from the photoconductivity spectra.     

Resonant Γ-<Emphasis Type="Italic">X</Emphasis> tunneling in single-barrier GaAs/AlAs/GaAs heterostructures

The electron transport through single-barrier GaAs/AlAs/GaAs heterostructures is studied. This transport is caused by resonant tunneling between the two-dimensional states related to the Γ valley of the GaAs conduction band and various two-or zero-dimensional donor states related to the lower X valleys of the AlAs conduction band. The resonant electron tunneling both via various two-dimensional states related to the X_z and X_xy valleys in AlAs (the X_z and X_xy states) and via related states of Si donors X _z ^D and X _xy ^D was observed. This circumstance made it possible to determine the binding energies of these states (E_B(X _z ^D )≈50 meV and E_B(X _xy ^D )≈70 meV, respectively) directly from the results of identification of resonance features in transport characteristics. An analysis of the structure of experimental resonances corresponding to tunneling between the Γ and X Landau levels in a magnetic field made it possible to determine the transverse effective mass in the X valleys of AlAs (m_t=(0.2±0.02)m₀). An additional fine structure of donor resonances is observed in experimental transport characteristics. This fine structure is caused by resonant tunneling of electrons through the states of the donors that are located in various atomic layers of the AlAs barrier (in the growth direction) and therefore have different binding energies.     

Test Data Compression for System-on-chip using Flexible Runs-aware PRL Coding

This paper presents a flexible runs-aware PRL coding method whose coding algorithm is simple and easy to implement. The internal 2^-n -PRL coding iteratively codes 2 ⁿ runs of compatible or inversely compatible patterns inside a single segment. The external N-PRL coding iteratively codes flexible runs of compatible or inversely compatible segments across multiple segments. The decoder architecture is concise. The benchmark circuits verify the flexible runs-aware PRL coding method, the experimental results show it obtains higher compression ratio and shorter test application time.     

A study of the effect of oxygen on the intensity of erbium photoluminescence in amorphous SiO<Subscript>x</Subscript>:(H,Er) films formed by DC magnetron sputtering

The effect of oxygen on the intensity of erbium photoluminescence at λ=1.54 μm in amorphous a-SiO_x:H(Er) films formed by dc magnetron sputtering was studied. The oxygen content in the gaseous phase ranged from 0.1 to 12 mol %, with other parameters of deposition remaining constant. Analysis of an a-Si:(H, Er, O) system showed that the range of homogeneity of amorphous a-SiO_x:H(Er) is retrograde (T=const). The range of homogeneity can be conventionally divided into two portions, each of which should contain either of two differently charged [Er-O] ⁿ⁻ and [Er-O-Si-O] ^m− clusters (m>n). This inference is confirmed experimentally: in the range of oxygen concentrations amounting to 5.5–8 mol % in the plasma, unusual associative processes take place probably directly above the growing film surface; these processes are caused by the appearance of [Er-O-Si-O] ^m− clusters in the plasma and at the surface. It is these processes that account for the intensification of erbium photoluminescence as the oxygen content increases above 5.5 mol %. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 37, No. 7, 2003, pp. 853–859. Original Russian Text Copyright ? 2003 by Undalov, Terukov, Gusev, Kudoyarova.     

Analysis of a high frequency and wide bandwidth active polyphase filter based on CMOS inverters

An active polyphase filter capable of high frequency quadrature signal generation has been analyzed. The resistors of the classical passive polyphase filter have been replaced by transconductors, CMOS inverters (F. Tillman and H. Sjöland, Proceedings of the Norchip Conference (pp. 12–15), Nov. 2005; Analog Integrated Circuits and Signal Processing, 50(1) 7–12, 2007). A three-stage 0.13 μm CMOS active polyphase filter has been designed. Simulations with a differential input signal show a quadrature error less than 1° for the full stable input voltage range for frequencies from 6 GHz to 14 GHz. Phase errors in the differential input signal are suppressed at least three times at the output. Corner simulations at 10 GHz show a maximum phase error of 3° with both n- and pMOS slow, in all other cases the error is less than 0.75°. The three-stage filter consumes 34 mA from a 1.2 V supply. To investigate the robustness of the filter to changes in inverter delay, an inverter model was implemented in Verilog-A. Linear c _in and g _in were used, whereas g _m , c _out , and g _out were non-linear. It was found that the filter could tolerate substantial delays. Up to 40° phase shift resulted in less than 1.5° quadrature phase error at the output.     

A Classification Approach for an Accurate Analog/RF BIST Evaluation Based on the Process Parameters

Specifications of Radio Frequency (RF) analog integrated circuits have increased strictly as their applications tend to be more complicated and high test cost demanding. This makes them very expensive due to an increased test time and to the use of sophisticated test equipment. Alternative test measures, extracted by means of Built-In Self Test (BIST) techniques, are useful approaches to replace standard specification-based tests. One way to evaluate the efficiency of the CUT measures at the design stage is by estimating the Test Escapes (T _E ) and the Yield Loss (Y _L ) at ppm level. Unfortunately, an important number of Monte Carlo simulations must be run in order to guarantee their accuracy. For certain types of circuits, this requires many months or even years to generate millions of circuits. To overcome this limitation, we present in this paper a new technique where a small number of simulations is sufficient to reach an important precision. This method is based on a classification using machine learning methods, such as SVM and Neural Networks based classifiers to determine pass/fail regions. The proposed approach requires a few number of simulations only to determine the region separating the process parameters generating good and faulty, or pass and fail circuits. Then only this region is needed to estimate the test metrics without running any additional simulation. The proposed methodology is illustrated for the evaluation of a filter BIST technique.     

Computationally Efficient Motion Estimation Algorithm for HEVC

In this paper, we present a novel computationally efficient motion estimation (ME) algorithm for high-efficiency video coding (HEVC). The proposed algorithm searches in the hexagonal pattern with a fixed number of search points at each grid. It utilizes the correlation between contiguous pixels within the frame. In order to reduce the computational complexity, the proposed algorithm utilizes pixel truncation, adaptive search range, sub-sampling and avoids some of the asymmetrical prediction unit techniques. Simulation results are obtained by using the reference software HM (e n c o d e r_l o w d e l a y_P_m a i n and e n c o d e r_r a n d o m a c c e s s_m a i n profile) and shows 55.49% improvement on search points with approximately the same PSNR and around 1% increment in bit rate as compared to the Test Zonal Search (TZS) ME algorithm. By utilizing the proposed algorithm, the BD-PSNR loss for the video sequences like B a s k e t b a l l P a s s_416 × 240@50 and J o h n n y_1280 × 720@60 is 0.0804 dB and 0.0392 dB respectively as compared to the HM reference software with the e n c o d e r_l o w d e l a y_P_m a i n profile.     

On the density-of-states effective mass and charge-carrier mobility in heteroepitaxial films of bismuth telluride and Bi<Subscript>0.5</Subscript>Sb<Subscript>1.5</Subscript>Te<Subscript>3</Subscript> solid solution

It is shown that the Seebeck coefficient α, the power factor α²σ, and the density-of-states effective mass m/m ₀ in heteroepitaxial films of Bi0.5Sb1.5Te3 solid solution are higher than the corresponding characteristics of bulk thermoelectric materials. The elevated values and weak temperature dependences of these parameters lead to a rise in the parameter proportional to the effective mass, the charge-carrier mobility, and the figure of merit. The character of change in α, α²σ, and m/m ₀ is determined by the peculiarities of the mechanism of charge-carrier scattering, the anisotropy of the constant-energy surface, and the possible influence of topological surface states of Dirac fermions in the films.     

Improvement in Thermoelectric Performance of SnS Due to Electronic Structure Modification Under Biaxial Strain

Ab-initio calculations using the full potential linearized augmented plane-wave technique and the semi-classical Boltzmann theory are used to study thermoelectric properties of unstrained SnS and at 1%, 2% and 3% applied biaxial tensile (BT) strain. The studies are carried out at 800 K for p-type and n-type carriers. For an increase in BT strain, lattice constants of SnS change causing changes in the band structure and increase in the band gap which in turn modifies thermoelectric coefficients. In the case of unstrained SnS, the maximum thermopower (S) obtained is 426 μV/K at carrier concentration 5.40?×?10¹⁸ cm^?3 for p-type carriers and 435 μV/K at carrier concentration 1.68?×?10¹⁸ cm^?3 for n-type carriers. At 3% applied BT strain, S is increased to 696 μV/K at carrier concentration 4.61?×?10¹⁷ cm^?3 for p-type carriers and 624 μV/K at carrier concentration 3.21?×?10¹⁷ cm^?3 for n-type carriers. The power factor (PF) increases?～?2 times at 3% BT strain as compared to unstrained SnS, and it is 6.20 mW K^?2 m^?1 for p-type carriers. For n-type carriers, PF at 3% applied BT is slightly less than the PF for unstrained SnS, which is 6.81 mW K^?2 m^?1. For both types of carriers, the figure of merit (ZT) is found to be?～?1.5 for unstrained SnS. For p-type carriers ZT is enhanced 1.4 times at 3% applied BT strain as compared to that of unstrained SnS. However, for n-type carriers, ZT does not change drastically with increase in BT strain.     

Electrical properties of <Emphasis Type="Italic">n-</Emphasis>GaN/<Emphasis Type="Italic">p</Emphasis>-SiC heterojunctions

Epitaxial GaN layers were grown by hydride vapor phase epitaxy (HVPE) on commercial (CREE Inc., USA) p⁺-6H-SiC substrates (Na ? Nd ≈ 7.8 × 10¹⁷ cm^s?3) and n⁺-6H-SiC Lely substrates with a predeposited p⁺-6H-SiC layer. A study of the electrical properties of the n-GaN/p-SiC heterostructures obtained confirmed their fairly good quality and demonstrated that the given combination of growth techniques is promising for fabrication of bipolar and FET transistors based on the n-GaN/p-SiC heterojunctions.