Versatile analog squarer and multiplier free from body effect

This paper proposes the analog CMOS squarer and the four-quadrant analog CMOS multiplier. The major advantages of the proposed circuits are low voltage supply, multifunction of output, and insensitive to the threshold voltage variation caused by body effect. The versatile squarer has two inputs (V _in and I _in ). Its output can be the square of V _in or the square of I _in . The versatile four-quadrant multiplier has four inputs (V _X , I _X , V _Y , and I _Y ). Its output can be the product of V _X and V _Y , the product of I _X and I _Y , the product of V _X and I _Y , or the product of V _Y and I _X . Therefore, the proposed circuits can be applied more than conventional circuits and have good performance. Second-order effects and frequency response are analyzed. Simulation results have verified the workability of the circuits. Experimental results are done to confirm the operation of the circuits.     

A direct-construction approach to multidimensional realization and LFR uncertainty modeling

This article proposes a direct-construction realization procedure that simultaneously treats all the involved variables and/or uncertain parameters and directly generates an overall multidimensional (n-D) Roesser model realization or linear fractional representation (LFR) model for a given n-D polynomial or causal rational transfer matrix. It is shown for the first time that the realization problem for an n-D transfer matrix G(z ₁, . . . , z _n ), which is assumed without loss of generality to be strictly causal and given in the form of G(z ₁, . . . , z _n )=N _r (z ₁, . . . , z _n )D _r ^?1 (z ₁,..., z _n ) with D _r (0, . . . , 0)=I and N _r (0, . . . , 0)  = 0, can be essentially reduced to the construction of an admissible n-D polynomial matrix Ψ for which there exist real matrices A, B, C such that N _r (z ₁, . . . , z _n ) = CZΨ and Ψ D _r ^?1 (z ₁, . . . , z _n ) = (I ? AZ)^?1 B with Z being the corresponding variable and/or uncertainty block structure, i.e., ${Z={\rm diag} \{z_1I_{r_1},\ldots,z_nI_{r_n} \}}$ . This important fact reveals a substantial difference between the 1-D and n-D (n ≥  2) realization problems as in the 1-D case Ψ can only be a monomial matrix and never a polynomial one. Necessary and sufficient conditions for Ψ to satisfy the above restrictions are given and algorithms are proposed for the construction of such an admissible n-D polynomial matrix Ψ with low order (for an arbitrary but fixed field of coefficients) and the corresponding realization. Symbolic and numerical examples are presented to illustrate the basic ideas as well as the effectiveness of the proposed procedure.     

Hot electron noise and g-r noise in short-channel JFETs

Hot electron noise in short-channel JFETs is measured above 150°K and generation-recombination noise due to donors is measured below 120°K, where it predominates over the first. The hot electron noise increases with increasing V_GS - V_P for a given temperature T and increasing with decreasing T at a given V_GS - V_P. The g-r noise in donors increases very rapidly with decreasing temperature and is found to be governed by an activation energy between E₀ and 2E₀, where E₀ is the activation energy of the donors. The theories of these effects can qualitatively explain the data; for the g-r noise it must be taken into account that the activation energy of the donors decreases with increasing electric field (Poole-Frenkel effect).     

Growth of Ge1 − x Sn x solid solution films and study of their structural properties and some of their photoelectric properties

From the charge state and closeness of the covalent radii of molecules of the solution-forming components, the possibility of the formation of the solutions Si_{1 ? x} Ge _x , Si_{1 ? x} Sn _x , (Si₂)_{1 ? x} (SnC) _x , Ge_{1 ? x} Sn _x , (Ge₂)_{1 ? x} (SiSn) _x , (SiC)_{1 ? x} (GeC) _x , (GeC)_{1 ? x} (SnC) _x , and (SiGe)_{1 ? x} (SnC) _x based on chemical elements of Group IV has been predicted. Single-crystal films of the substitutional solid solution Ge_{1 ? x} Sn _x (0 ≤ x ≤ 0.03) have been grown on Ge substrates by liquid-phase epitaxy. X-ray diffraction patterns, spectral photosensitivity, and the I–V characteristics of the obtained n-Ge-p-Ge_{1 ? x} Sn _x heterostructures have been investigated. The lattice parameters of the epitaxial film and the substrate a _f = 5.6812 Å and a _s = 5.6561 Å have been determined. The spectral photosensitivity of the n-Ge-p-Ge_{1 ? x} Sn _x heterostructures encompasses the photon energy range from 0.4 to 1.4 eV. It is shown that the forward portion of the I–V characteristics of the investigated structures at low voltages (up to 0.5 V) is described by the exponential dependence I = I ₀exp(qV/ckT) and at high voltages (V > 0.5 V), by the power dependence I ∝ V ^α with the values α = 2 at V = (0.5–0.9) V, α = 1.3 at V = (0.9–1.4) V, and α = 2 at V > 1.4 V. The experimental data are explained within the double injection model for the n-p-p structure using the drift mechanism of current transport in the ohmic relaxation mode taking into account the inertia of the electron exchange inside a recombination complex.     

Temperature and frequency dependent electrical and dielectric properties of Al/SiO2/p-Si (MOS) structure

The electrical and dielectric properties of Al/SiO₂/p-Si (MOS) structures were studied in the frequency range 10 kHz-10 MHz and in the temperature range 295-400 K. The interfacial oxide layer thickness of 320 Å between metal and semiconductor was calculated from the measurement of the oxide capacitance in the strong accumulation region. The frequency and temperature dependence of dielectric constant (ε′), dielectric loss (ε″), dielectric loss tangent (tan δ) and the ac electrical conductivity (σ_ac) are studied for Al/SiO₂/p-Si (MOS) structure. The electrical and dielectric properties of MOS structure were calculated from C-V and G-V measurements. Experimental results show that the ε′ and ε″ are found to decrease with increasing frequency while σ_ac is increased, and ε′, ε″, tan δ and σ_ac increase with increasing temperature. The values of ε′, ε″ and tan δ at 100 kHz were found to be 2.76, 0.17 and 0.06, respectively. The interfacial polarization can be more easily occurred at low frequencies, and the number of interface state density between Si/SiO₂ interface, consequently, contributes to the improvement of dielectric properties of Al/SiO₂/p-Si (MOS) structure. Also, the effects of interface state density (N_ss) and series resistance (R_s) of the sample on C-V characteristics are investigated. It was found that both capacitance C and conductance G were quite sensitive to temperature and frequency at relatively high temperatures and low frequencies, and the N_ss and R_s decreased with increasing temperature. This is behavior attributed to the thermal restructuring and reordering of the interface. The C-V and G/ω-V characteristics confirmed that the N_ss, R_s and thickness of insulator layer (δ) are important parameters that strongly influence both the electrical and dielectric parameters and conductivity in MOS structures.     

Direct, prediction- and smoothing-based Kalman and particle filter algorithms

We address the recursive computation of the filtering probability density function (pdf) p_n|n in a hidden Markov chain (HMC) model. We first observe that the classical path p_n−1|n−1→p_n|n−1→p_n|n is not the only possible one that enables to compute p_n|n recursively, and we explore the direct, prediction-based (P-based) and smoothing-based (S-based) recursive loops for computing p_n|n. We next propose a common methodology for computing these equations in practice. Since each path can be decomposed into an updating step and a propagation step, in the linear Gaussian case these two steps are implemented by Gaussian transforms, and in the general case by elementary simulation techniques. By proceeding this way we routinely obtain in parallel, for each filtering path, one set of Kalman filter (KF) equations and one generic sequential Monte Carlo (SMC) algorithm. Finally we classify in a common framework four KF (two of which are original), which themselves can be associated to four generic SMC algorithms (two of which are original). We finally compare our algorithms via simulations. S-based filters behave better than P-based ones, and within each class of filters better results are obtained when updating precedes propagation.     

Electrical and thermoelectric properties of ZnO under atmospheric and hydrostatic pressure

Temperature (for T = 77–400 K) and pressure (for P ≤ 8 GPa) dependences of conductivity σ(T,P). Hall coefficient R _H(T, P), and Seebeck coefficient Q(T) were studied in single-crystal n-ZnO samples with the impurity concentration N _i = 10¹⁷ ? 10¹⁸ cm^?3 and free-electron concentration n = 10¹³?10¹⁷ cm^?3. Single crystals were grown by the hydrothermal method. Dependence of the ionization energy of a shallow donor level on the impurity concentration E _d1(N _d) is determined, along with the pressure coefficients for the ionization energy ?E _d1/?P and static dielectric constant ?x/?P. A deep defect level with the energy E _d2 = 0.3 eV below the bottom of the conduction band is found. The electron effective mass is calculated from the obtained data on the kinetic coefficients R _H(T) and Q(T).     

Origin of forward bias capacitance peak and intersection behavior of C and G/w of Ag/p-InP Schottky barrier diodes

Frequency-dependent electrical characteristics of Ag/p-InP diodes have been determined using impedance spectroscopy at room temperature. Series resistance (R_s) and interface state(s) (N_ss) values were extracted from capacitance (C) and conductance (G/w) data using the Nicollian and Goetzberger and Hill–Coleman methods, respectively. C and G/w data were also corrected in the whole measured bias voltage range to obtain real diode capacitance C_c and conductance G_c values in order to see the effects of R_s. Both the C–V and R_s–V plots showed anomalous peak in depletion region especially at low frequencies due to the existence of N_ss. C–V and G/w–V plots crossed at a certain bias voltage and this point shifted toward negative bias voltages with increasing frequency and then disappeared at 3 MHz. Also, decrease in C values corresponds to an increase in G/w values in the same bias voltages.     

Recombination and trapping centers in pure and doped TlBr crystals

TlBr is a promising wide-gap semiconductor for developing γ-radiation detectors. One of the limiting factors in developing the technology of detectors is the lack of experimentally determined trapping and recombination centers. In this paper, a generalized model of the formation and behavior of intrinsic defects in pure and doped TlBr single crystals is presented. The relation of intrinsic defects to growth conditions and electrical properties is determined. The previously obtained temperature dependences of the photoconductivity, the data of current deep level transient spectroscopy and microcathodoluminescence, and the kinetic characteristics of the photoconductivity are used as objects of analysis. It is shown that the compensation of charged centers control the transport properties of charge carriers. In compensated doped TlBr crystals, the product of the mobility and lifetime can reach μτ = 5 × 10^?4 cm² V^?1. The energy-level diagram of local levels in pure and doped TlBr crystals is proposed. The ionization energies of major structural and impurity defects in TlBr, i.e., the anion vacancy V _a ⁺ , cation vacancy V _c ^? , and Pb²⁺, O^2?, S^2? ions, are determined. The energy position of a single anion vacancy V _a ⁺ is E _c ? 0.22 eV. The energy level of the cation vacancy is E _v + 0.85 eV for a single cation vacancy and E _v + 0.58 eV for a vacancy incorporated into the {Pb²⁺ V _c ^? }⁰ complex. The ionization energy of the Pb²⁺ Coulomb trap is E _c ? 0.08 eV in doped TlBr crystals.     

An improved model to explain ohmic contact resistance of f-GaAs and other semiconductors

A model is proposed which explains the inverse proportionality between specific contact resistance ϱ_c and the carrier concentration (N_D) of n-GaAs ohmic contact obtained experimentally very well and can be extended to the ohmic contact of other semiconductors. This model assumes that ϱ_c is composed of two parts ϱ_c1 and ϱ_c2. The contact resistivity ϱ_c1 is due to the contact between the alloy and the underlying heavily doped contact region (N_DC for n-type contact, N_AC for p-type contact) formed by doping from the contact alloys during annealing. The contact resistivity ϱ_c2 is caused by the barrier height (Φ₂) of the high-low junction between the heavily doped contact region and the bulk material. There are two aspects: (1) If bulk material is degenerated, i.e. N_D >N_C (N_C: effective density of states in conduction band) or N_A >N_V (N_V: effective density of states in valence band), the barrier height Φ₂ vanishes and ifϱ_(c) is mainly determined by ifϱ_c1 which depends solely on concentrations N_DC and N_AC. It is calculated theoretically. (2) When the bulk material is lightly doped, i.e. N_D < N_Cor N_A < N_V, then Φ₂ appears and increases with the decreasing of N_D(N_A). If N_DC or N_AC are high enough, the field emission is the main mechanism to control the carrier transport between the contact alloy and the underlying layer. In this case ϱ_c is predominantly determined by ϱ_c2 and an inverse proportionality between ϱ_c and N_D or N_A can be found.     

Excess high frequency noise and flicker noise in MOSFETs

The noise parameter α=R_ng_m, where R_n is the noise resistance and g_m the transconductance, was measured for n- and p-channel MOSFETs as a function of frequency with the temperature T as a parameter. At lower frequencies α varies as 1/f, as expected for flicker noise, whereas at higher frequencies α attains a limiting value α_∞ that is larger than expected for thermal noise. Arguments are presented whether this high-frequency noise can be hot electron noise. The flicker noise resistance R_mf has a much stronger temperature dependence for n-channel than for p-channel devices; this is related to the energy dependence of the surface state distribution in the forbidden gap.     

Formation and annealing of metastable (interstitial oxygen)-(interstitial carbon) complexes in n- and p-type silicon

It is shown experimentally that, in contrast to the stable configuration of (interstitial carbon)-(interstitial oxygen) complexes (C _i O _i ), the corresponding metastable configuration (C _i O _i *) cannot be found in n-Si based structures by the method of capacitance spectroscopy. The rates of transformation C _i O _i * →C _i O _i are practically the same for both n- and p-Si with a concentration of charge carriers of no higher than 10¹³ cm^?3. It is established that the probabilities of the simultaneous formation of stable and metastable configurations of the complex under study in the case of the addition of an atom of interstitial carbon to an atom of interstitial oxygen is close to 50%. This is caused by the orientation dependence of the interaction potential of an atom of interstitial oxygen with an interstitial carbon atom, which diffuses to this oxygen atom.     

On threshold and flat-band voltages for MOS devices with polysilicon gate and nonuniformly doped substrate

Expressions for the flat-band voltage V_FB and threshold voltage V_T for MOS devices with polysilicon gate and nonuniformly doped substrate are given. The role of metal-semiconductor contacts and the assumptions involved in the analysis are discussed. Both V_FB and V_T have three extra terms over the conventional expressions, two terms result from nonuniform doping and one is due to a voltage drop in the gate produced by space charge. Contrasts are made to devices with metal gates and uniformly doped substrates. The commonly used expression for mobile channel charge in terms of gate voltage is clarified.     

Minority carrier lifetimes in silicon solar cells determined from spectral and transient measurements

Measurements of the spectral collection efficiency and short circuit current decay rate following an X-ray pulse have been made on three types of single crystal silicon solar cells. The cell types were n⁺ - p, p⁺ - n, and p⁺ - n - n⁺ with base resistivities of 0.3, 10 and 10 Ω-cm, respectively. Minority carrier lifetimes were determined from both experiments using analytical or device code calculations, as required. For the n⁺ - p and p⁺ - n cells, nominal lifetimes of 2 and 5 ωsec, respectively, were obtained. A lifetime greater than 100 ωsec was inferred for the p⁺ - n - n⁺ device. This value represents a minimum estimate since our analysis is inaccurate when the diffusion length exceeds the cell thickness, as is the case here. The difference in base lifetime for the p⁺ - n and p⁺ - n - n⁺ structures is attributed to gettering during the phosphorus diffusion to form the back surface field layer.     

Multiple error detection and identification via signature analysis

Signature analysis has been used widely for fault detection as a part of Built-In Self Test (BIST). In this paper we show how signature analysis can be used not only for fault detection but also for identification of multiple errors produced by faults in the circuits under test. We construct Signature Analysis Registers (SARs) to detect and identify any specified number of errors in the input polynomials by choosing proper characteristic polynomials. To detect and identifyr errors in an input bit stream ofm bits, we use a polynomialg _r (x)=1cm (f ₁ (x), f ₃ (x), ..., f _2r?1 (x)) as the characteristic polynomial for the SAR for any polynomialf ₁ (x), where lcm represents the least common multiple of polynomials al $$fi(x) = Res_t (f_1 (t),x - t^i ), i = 3,...,2r - 1,$$ Res _t denotes thet-Resultant, andm is less than the order off ₁ (x). Given a faulty signature produced by an SAR constructed as described, we present an algorithm for the identification of the actual error bits in the input polynomial to the SAR. We also extend the use of BCH codes for error detection and correction to include nonprimitive polynomials.     

On completeness and multi-channel sampling

A bandlimited input x is applied as a common input to m linear time-invariant filters (channels) which are ‘independent’ in a certain sense. We investigate, from a unified point of view using the concept of completeness, the problem of uniquely reconstructing the input x for all time values from samples of the m outputs, each output being sampled at the uniform rate of σ/gqm samples/second, where σ is the positive frequency bandwidth of the input signal.For the lowpass input case and independent channels, perfect reconstruction is always possible; similarly for the case of a bandpass input and an even number of channels, recovery of the input can also be accomplished at a rate of σ/mπ samples/second. However, for an odd number m of channels and a bandpass input, it is shown that the rate σ/mπ samples/second at the outputs no longer suffices to determine the input uniquely unless 2ω₀m/σ is an odd integer, a constraint on the relation between the center frequency of the band, ω₀, and the bandwidth σ. To obtain a sampling theorem when the number of channels is odd and in the absence of such a positioning constraint, a higher sampling rate per channel must be employed.In those cases which permit a unique determination of the input from samples of the output channels, it is shown that a linear scheme involving m linear time-invariant post-filters can be used to effect the input reconstruction.     

On the profile of frequency and voltage dependent interface states and series resistance in (Ni/Au)/Al0.22Ga0.78N/AlN/GaN heterostructures by using current-voltage (I-V) and admittance spectroscopy methods

In order to explain the experimental effect of interface states (N_ss) and series resistance (R_s) of device on the non-ideal electrical characteristics, current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G/ω-V) characteristics of (Ni/Au)/Al_0.22Ga_0.78N/AlN/GaN heterostructures were investigated at room temperature. Admittance measurements (C-V and G/ω-V) were carried out in frequency and bias voltage ranges of 2 kHz-2 MHz and (−5 V)-(+5 V), respectively. The voltage dependent R_s profile was determined from the I-V data. The increasing capacitance behavior with the decreasing frequency at low frequencies is a proof of the presence of interface states at metal/semiconductor (M/S) interface. At various bias voltages, the ac electrical conductivity (σ_ac) is independent from frequencies up to 100 kHz, and above this frequency value it increases with the increasing frequency for each bias voltage. In addition, the high-frequency capacitance (C_m) and conductance (G_m/ω) values measured under forward and reverse bias were corrected to minimize the effects of series resistance. The results indicate that the interfacial polarization can more easily occur at low frequencies. The distribution of N_ss and R_s is confirmed to have significant effect on non-ideal I-V, C-V and G/ω-V characteristics of (Ni/Au)/Al_0.22Ga_0.78N/AlN/GaN heterostructures.     

Crystal structure and band gap of AlGaAsN

Quantum dielectric theory is applied to the quaternary alloy Al_xGa_1−xAs_1−yN_y to predict its electronic properties as a function of Al and N mole fractions. Results are presented for the expected crystal structure, minimum electron energy band gap, and direction in k-space of the band gap minimum for all x and y values. The results suggest that, for a proper choice of x and y, Al_xGa_1−xAs_1−yN_y could exhibit certain advantages over Al_xGa_1−xAs when utilized in field-effect transistor structures.     

Temperature dependence of Al/Ti-based Ohmic contact to GaN devices: HEMT and MOSFET

In this paper two types of Al/Ti-based Ohmic contacts to Gallium Nitride (GaN) based devices are presented; ImplantedN⁺GaN (like the ones found in the Source/Drain of GaN Metal Oxide Semiconductor Field Effect Transistors-MOSFET) and heterojunction (HJ) AlGaN/GaN contacts (Source/Drain of High Electron Mobility Transistors-HEMT). Sheet resistance (R_sh) and contact resistance (R_c) have been investigated in the temperature (T) range of 25-250 °C. It was found that the R_sh (850/700 Ω□) (25/250 °C) and R_c (2.2/0.7 Ωmm) decrease with T for ImplantedN⁺GaN contact and R_sh (400/850 Ω□) and R_c (0.2/0.4 Ωmm) (weakly for R_c) increase with T for HJAlGaN/GaN contact. Numerical computation based models are used to determine the theoretical R_sh and R_c behavior with T and to fit the experimental values.     

Input Locality and Hardness Amplification

We establish new hardness amplification results for one-way functions in which each input bit influences only a small number of output bits (a.k.a. input-local functions). Our transformations differ from previous ones in that they approximately preserve input locality and at the same time retain the input size of the original function. Let f:{0,1} ⁿ →{0,1} ^m be a one-way function with input locality d, and suppose that f cannot be inverted in time $\exp(\tilde{O}(\sqrt{n}\cdot d))$ on an ε-fraction of inputs. Our main results can be summarized as follows:

• If f is injective then it is equally hard to invert f on a (1?ε)-fraction of inputs.
• If f is regular then there is a function g:{0,1} ⁿ →{0,1} ^m+O(n) that is d+O(log³ n) input local and is equally hard to invert on a (1?ε)-fraction of inputs.

A natural candidate for a function with small input locality and for which no sub-exponential time attacks are known is Goldreich’s one-way function. To make our results applicable to this function, we prove that when its input locality is set to be d=O(logn) certain variants of the function are (almost) regular with high probability. In some cases, our techniques are applicable even when the input locality is not small. We demonstrate this by extending our first main result to one-way functions of the “parity with noise” type.