Arsenic Diffusion Study in HgCdTe for Low <Emphasis Type="Italic">p</Emphasis>-Type Doping in Auger-Suppressed Photodiodes

Controllable p-type doping at low concentrations is desired for multilayer HgCdTe samples in a P ⁺/π/N ⁺ structure due to the promise of suppressing Auger processes, and ultimately reduced dark current for infrared detectors operating at a given temperature. In this study, a series of arsenic implantation and annealing experiments have been conducted to study diffusion at low Hg partial pressure with the goal of achieving effective control over dopant profiles at low concentration. Arsenic dopant profiles were measured by secondary ion mass spectroscopy (SIMS), where diffusion coefficients were extracted with values ranging between 3.35 × 10⁻¹⁶ cm² s⁻¹ and 6 × 10⁻¹⁴ cm² s⁻¹. Arsenic diffusion coefficients were found to vary strongly with Hg partial pressure and HgCdTe alloy composition, corresponding to variations in Hg vacancy concentration.     

A simple CMOS process compatible high performance parallel-stacked spiral inductor for advanced RF analog circuit applications

A high Q on-chip inductor with some unique structures has been fabricated with 0.13 μm CMOS compatible process for the first time. The unique structures including parallel stacked, line via between inter-metal layers, and use the top signal pad as the under path of the inductor instead of conventional bottom signal pad. These structures offer advantages of reducing resistance, high Q value, simple preparing process and small chip area. Experimental results show that the measured peak Q and peak-Q frequency can attain 7.06 and 1.8 GHz, respectively for the structure with four metal layers in parallel, 15 μm in metal width, 5.5 turns in wire number,and an area of 204×240 μm². The results have a better potential for advanced mobile communication applications.     

Evaluation of Diffusion Barrier Between Lead-Free Solder Systems and Thermoelectric Materials

The intermetallic compound SnTe rapidly formed at interfaces between p-type bismuth telluride (Bi_0.5Sb_1.5Te₃) thermoelectric materials and lead-free solders. The intermetallic compound influences the mechanical properties of the joints and the reliability of the thermoelectric modules. Various lead-free solder alloys, Sn-3.5Ag, Sn-3Ag-0.5Cu, Sn-0.7Cu, and Sn-2.5Ag-2Ni, were used to investigate the interfacial reactions. The results thus obtained show that Ag and Cu preferentially diffused into the Te-rich phase in Bi_0.5Sb_1.5Te₃, so layers of Ag-Te and Cu-Te compounds could not form an effective diffusion barrier. Electroless nickel-phosphorus was plated at the interfaces to serve as a diffusion barrier, and the (Cu,Ni)₆Sn₅ compound formed instead of SnTe. Furthermore, the intermetallic compound NiTe formed between nickel- phosphorus and Bi_0.5Sb_1.5Te₃ and also served as a diffusion barrier. A plot of thickness as a function of annealing time yielded the growth kinetics of the intermetallic compounds in the thermoelectric material systems. The activation energy for the growth of the NiTe intermetallic compound is 111 kJ/mol.     

Sidelobes Due to Periodic Amplitude and Phase Errors in the Aperture Field of a Radial Waveguide Pin-Fed Array Antenna

The location and level of the sidelobes of a radial waveguide pin-fed array antenna, which stem from periodic amplitude and phase errors in the actual antenna aperture field, are derived based on a simple model of a line source as well as the pertinent model of a circular aperture. The theoretical results are verified by comparisons with numerical and measured data     

Point Defects in Pb-, Bi-, and In-Doped CdZnTe Detectors: Deep-Level Transient Spectroscopy (DLTS) Measurements

We studied, by current deep-level transient spectroscopy (I-DLTS), point defects induced in CdZnTe detectors by three dopants: Pb, Bi, and In. Pb-doped CdZnTe detectors have a new acceptor trap at around 0.48?eV. The absence of a V_Cd trap suggests that all Cd vacancies are compensated by Pb interstitials after they form a deep-acceptor complex [[Pb_Cd]⁺-V _Cd ^2? ]^?. Bi-doped CdZnTe detectors had two distinct traps: a shallow trap at around 36?meV and a deep donor trap at around 0.82?eV. In detectors doped with In, we noted three well-known traps: two acceptor levels at around 0.18?eV (A-centers) and 0.31?eV (V_Cd), and a deep trap at around 1.1?eV.     

A Minimax Chebyshev Estimator for Bounded Error Estimation

We develop a nonlinear minimax estimator for the classical linear regression model assuming that the true parameter vector lies in an intersection of ellipsoids. We seek an estimate that minimizes the worst-case estimation error over the given parameter set. Since this problem is intractable, we approximate it using semidefinite relaxation, and refer to the resulting estimate as the relaxed Chebyshev center (RCC). We show that the RCC is unique and feasible, meaning it is consistent with the prior information. We then prove that the constrained least-squares (CLS) estimate for this problem can also be obtained as a relaxation of the Chebyshev center, that is looser than the RCC. Finally, we demonstrate through simulations that the RCC can significantly improve the estimation error over the CLS method.     

Hamilton-Jacobi skeleton on cortical surfaces

In this paper, we propose a new method to construct graphical representations of cortical folding patterns by computing skeletons on triangulated cortical surfaces. In our approach, a cortical surface is first partitioned into sulcal and gyral regions via the solution of a variational problem using graph cuts, which can guarantee global optimality. After that, we extend the method of Hamilton-Jacobi skeleton to subsets of triangulated surfaces, together with a geometrically intuitive pruning process that can trade off between skeleton complexity and the completeness of representing folding patterns. Compared with previous work that uses skeletons of 3-D volumes to represent sulcal patterns, the skeletons on cortical surfaces can be easily decomposed into branches and provide a simpler way to construct graphical representations of cortical morphometry. In our experiments, we demonstrate our method on two different cortical surface models, its ability of capturing major sulcal patterns and its application to compute skeletons of gyral regions.     

A new three-level soft-switched converter

A three-level, constant-frequency, isolated converter which employs a coupled inductor to achieve zero-voltage switching of the primary switches in the entire line and load range is described. Because the coupled inductor does not appear as a series inductance in the load current path, it does not cause a loss of duty cycle or severe voltage ringing across the output rectifiers. The operation and performance of the proposed converter was verified on a 1-kW prototype.     

Improved algorithms for the determination of turbo-code weight distributions

We discuss algorithms for determining exactly the lower terms of the weight distribution of a turbo code. Several improvements on the recently introduced algorithm by Garello et al. are outlined. The techniques presented in this letter improve the observed asymptotic complexity by a factor proportional to the information length. As an example, the improved algorithm is applied to the determination of the minimum distance of all universal mobile telecommunications system turbo codes. We further apply the improved algorithm to high-rate turbo codes using high-rate nonpunctured constituent codes. To reduce complexity, the constituent codes are represented by a minimal information bit-oriented trellis.     

A continuous-time /spl Sigma//spl Delta/ Modulator with reduced sensitivity to clock jitter through SCR feedback

This paper presents a means to overcome the high sensitivity of continuous-time sigma-delta (/spl Sigma//spl Delta/) modulators to clock jitter by using a modified switched-capacitor structure with resistive element in the continuous-time feedback digital-analog converter (DAC). The reduced sensitivity to jitter is both simulated and proven by measured results from two implemented third-order modulators. Additionally, the nonideal behavior is analyzed analytically and by simulations.