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Engaging underrepresented populations of women and minorities in engineering represents our greatest untapped resource for increasing the STEM workforce and its productivity. Guided by the research that shows that students' performance and experience in a first course in the discipline is predictive of retention of these students, we are adopting Merit workshops into our Introduction to Electronics course (one of our department's first-year courses). Merit workshops engage students in collaborative learning communities to improve students' sense of belonging in the department. In this work in progress paper, we will describe how we implemented our Merit workshops and provide some preliminary evaluations of the workshop.

Microelectronics manufacturers continue to subject a wide range of products or representative test vehicles to accelerated thermal cycling tests. Most such testing is focused on comparisons, whether among alternatives or to an established requirement. However, more often than commonly recognized such comparisons may not reflect the relative performances in service. In fact, most current models have been shown to fail to account for important systematic trends as well as being inconsistent with our current understanding of the failure rate controlling damage mechanism. An alternative mechanistically justified model for the thermal fatigue life of SnAgCu solder joints has been proposed. Damage and failure occurs by recrystallization of the large Sn grains across the high strain region of the joint, followed by crack growth along the resulting network of high angle grain boundaries. The recrystallization was shown to be the damage rate controlling mechanism, except for extremely high strain assemblies and/or harsh cycling conditions, i.e. if we can predict the recrystallization we can predict the number of cycles to failure. So far the model accounts for a variety of important trends and offers guidance as to the interpretation and generalization of accelerated test results. General extrapolations towards service conditions will, however, require the specific functional dependence of the rate of recrystallization on the stress and the precipitate distributions. Another potential difficulty is that constitutive relations are extracted from single sided creep experiments while the dislocation cell structures built up under cyclic loading are certain to be different. Furthermore, the repeated `annealing' during the high temperature dwell affects the hardening. Even if these effects could be ignored the ongoing evolution of the constitutive relations would still effectively prevent the extraction of the above-mentioned functional dependence from comparisons between thermal cycling results and FEM. A special experiment is ongoing in which stresses and strains on the solder joints can be controlled and measured directly, allowing the testing of individual assumptions underlying the proposed model. Preliminary results are presented and compared to results of thermal cycling across different temperature ranges.

Accurate estimation of PHY conditions would allow for better cross-layer resource management and provisioning. Unfortunately, most commercial-of-the-shelf (COTS) devices typically provide very limited information. For example, IEEE 802.15.4 Zigbee radios only provide received signal strength indicator (RSSI), link quality indicator (LQI) and noise floor readings, which are stored in frame check sequence (FCS) of MAC frames. In this paper, we revisit the issue of link quality prediction in IEEE 802.15.4 low rate wireless personal area networks (LR-WPAN) analytically and experimentally. By deciphering LQI readings available in Zigbee radios with CC2420 chipset, we demonstrate for the first time that LQI truly reflects the signal-to- noise ratio (SNR) at receiver. We also investigate the chip correlation (CORR) defined in CC2420 data sheet, and verify its relationship with LQI readings through measurement studies. Furthermore, in order to predict the instantaneous link quality for commodity Zigbee radios, we develop an inference model under different channel environments that uses instantaneous LQI readings as input. The proposed model is validated using extensive simulation and experimental study. We believe it will lead to more informed resource management decisions in WPANs.

Our general education course in digital information technology draws many students from academic disciplines outside science and mathematics. These students often struggle with the relevance of the course topics. To promote student motivation, we are modifying the course to better engage the students in the course topics via a method we term diversity harnessing. Diversity harnessing refers to the diversity in the students' personal interests and chosen academic disciplines. From the students' interests, we intend to gather applications and ideas and to quickly integrate this diverse student-driven subject matter back into the lectures, homework assignments, and examinations. Through diversity harnessing, we expect to find that students are more engaged in the course and that they apply the course content more effectively to their lives and careers beyond the end of the semester. We are assessing the effectiveness of diversity harnessing using both individual interviews and a standard course engagement questionnaire.

We present an investigation of the growth of InP based materials in a Multiwafer Planetary Reactor (R). A reactor suited for the simultaneous growth of 15/spl times/2", 8/spl times/3" or 5/spl times/4" wafers was used to grow InP, GaInAs and various GaInAsP compositions. As predicted by the theory of the Planetary Reactor (R) principle, excellent uniformities of all layer properties were found. Without any tuning of process parameters, thickness variations of /spl plusmn/1% or better were obtained. The compositional uniformity was also very good. This was confirmed by X-ray diffraction and PL mapping. Emission wavelength uniformities were in the 1 nm range. p- and n-type doping was also investigated. Sheet resistivity measurements on doped samples reveal uniformities around 1%.

The improvement in wafer yield to increase the amount of usable wafer area per epitaxy run is of paramount interest. One possibility would be to change the precursors just for the active layer of the device to combine the advantages of PH/sub 3/ and TBP in one structure. As TBP is known as already totally decomposed at 600 /spl deg/C as opposed to the case of PH/sub 3/ it could give a less temperature sensitive alternative to grow quaternary material for optoelectronic devices. On the other hand buffer and claddings can still be grown with the cheaper PH/sub 3/. This investigation, focuses on the wafer photoluminescence standard deviation (Std. Div) in a total of 14 laser test structure MOCVD runs. The goal is to check if there could be an advantage to using different precursors in one structure.

A reconfigurable flight control method is developed to be implemented on an Unmanned Aircraft (UA), a thirty percent scale model of the Cessna 150. This paper presents the details of the UAV platform, system identification, reconfigurable controller design, development, and implementation on the UA to analyze the performance metrics. A Crossbow Inertial Measurement Unit provides the roll, pitch and yaw accelerations and rates along with the roll and pitch. The 100400 mini-air data boom from spaceage control provides the airspeed, altitude, angle of attack and the side slip angles. System identification is accomplished by commanding preprogrammed inputs to the control surfaces and correlating the corresponding variations at the outputs. A Single Network Adaptive Critic, which is a neural network based optimal controller, is developed as part of a nonlinear flight control system. An online learning neural network is augmented to form an outer loop to reconfigure and supplement the optimal controller to guarantee a "practical stability" for the airplane. This paper also presents some simulations from the hardware-in-the-loop testing and concludes with an analysis of the flight performance metrics for the controller under investigation.

Studies of informational masking indicate that binaural listening provides benefit to speech understanding. This suggests that similar improvements to adaptive processing of binaural acoustic data may be achieved through dichotic presentation rather than the typical diotic presentation. Advanced signal processing for hearing aids often remove competing audio streams while retaining the undistorted audio stream of the target. In this paper, the frequency-domain minimum-variance distortionless-response (FMV) adaptive array processor [M. E. Lockwood, et al., 1999] is modified to provide a dichotic output. In addition to the suppression of the interference, dichotic presentation provides a perceived spatial separation between the target and maskers. Results from human subject testing support an improvement in speech intelligibility for near-optimal spatial separation in the algorithm. A real-time algorithm is currently under development to attempt to achieve a similar perception of spatial separation.

Pre-processing for hearing aids, such as adaptive beamforming, is sensitive to characteristics of the acoustic environment, in particular, reverberation. We conjecture that knowledge of the acoustic environment can aid selection of an optimal signal processing strategy. In this paper we present a method for estimation of direct-to-reverberant energy ratio from partial room responses to an impulsive sound at one receiver location, and of source distance, average absorption, reverberation time, and room volume as intermediate results.

The growth of highly carbon doped lattice matched InGaAs grown on semi-insulating InP is investigated in an AIX 2600G3 Multiwafer Planetary Reactor/spl reg/. A systematical investigation of the dependency of growth temperature, V/III ratio and doping concentration was conducted using CBr/sub 4/ as C precursor and AsH/sub 3/ as group V source. Subsequent to the growth an in-situ anneal step with TMAs was applied to activate carriers in the InGaAs layer. The highest achieved p-type carrier concentration is 6/spl times/10/sup 19/ cm/sup -3/ grown at 440/spl deg/C with a V/III ratio of 1.5. The layers were investigated by XRD, sheet resistance- and Hall-effect measurements.

An attribute of the decorrelating detector (DD) is the ease in which the a posteriori bit probabilities may be computed. In this paper, we use these a posteriori bit probabilities (e.g.. /spl pi//sub i/ /spl esdot/ P(b/sub i/ = +1 | y_)) to replace the standard a priori probabilities (e.g. /spl pi//sub i/ /spl esdot/ P(b/sub i/ = +1) /spl equiv/ 1/2 ) and find soft bit estimates that optimize particular cost functions under the Bayesian rule. The soft multiple access interference (MAI) bit estimates,are suitable for a parallel interference canceller (PIC) and create a new genre of CDMA detection algorithms. The bit error rate (BER) performance is shown to better approximate that of the optimal MAP detector than other soft PIC methods. The additive white Gaussian noise assumption (required for the interference canceller) is validated by the use of an adaptive beamformer.

Thompson [1980] showed that the eigenvector analysis required of Pisarenko's method of harmonic retrieval can be achieved on-line without explicit eigendecomposition. His method utilizes a unit-norm constrained adaptive filter to find and track a single vector that lies in the noise subspace. By tracking this vector without explicit formulation of the sample covariance matrix R or its eigendecomposition, the algorithm maintains a low computational cost. In this paper, Thompson's method is extended using a penalty method. The new algorithm seeks an orthonormal basis that spans the noise subspace. The computational complexity of the algorithm is then reduced to a more desirable level through the use of a relaxation technique. Once the noise subspace is constructed, one can compute the MUSIC power spectrum for an improved spectral estimate.

Results of the AIX 2600G3 planetary reactor(R) in the 35/spl times/2 inch configuration with Gas Foil Rotation(R) will be shown. Measurements including all seven 2 inch wafers of one satellite will be presented. As a further detailed study and tuning of the AIXTRON Planetary Reactor(R) system AIX 2600G3 in the 35 times 2 inch configuration, we investigated the depletion behaviour along the reactor radius using rotating, as well as intentionally fixed satellites. Very often doped DBR-structures are used as a mirror below the active region of the AlGaInP LED to increase the light output. So AlAs/GaAs distributed Bragg reflectors (DBR) were chosen to optimise the thickness homogeneity and gallium efficiency across the five 6 inch satellites in dependence of the total flow. Further on, we examined the influence of the total reactor pressure on the semiconductor layer composition via X-ray data of AlInP. To check the adjustments of our reactor configuration we chose the critical and very temperature sensitive material system AlGaInP, as well as AlGaInP-MQW structures.

GaInAs MISFETs with pyrolytic SiO/sub 2/ isolator on n- and p-GaInAs have been investigated with regard to analog and digital performance. The 1.7- mu m gate length MISFETs on n-GaInAs and p-GaInAs have transconductances of 100 mS/mm and 40 mS/mm, cutoff frequencies (f/sub T/) of 14 GHz and 2 GHz, and maximum frequencies of oscillation (f/sub max/) of 18 GHz and 6 GHz, respectively. Due to the self-aligned process and the better carrier confinement, the MISFETs on p-GaInAs show higher f/sub max//f/sub T/ values. An inverter on p-GaInAs with a high static voltage gain of -13.5 and high noise margin has been integrated to a 31-stage ring oscillator, proving the reproducibility of the technology with a pyrolytic SiO/sub 2/ isolator. The delay time of one stage is 6 ns, corresponding to an intrinsic frequency of 200 MHz, which shows that the operation point of the ring oscillator is not optimized. >

A single wafer reactor AIX 200/4 with improved performance for InP based materials has been developed. The AIX 200/4 reactor is a horizontal OMVPE reactor. The new designed reactor follows the widely used AIX 200 reactor. Additionally, it offers an enlarged diameter and some new features to influence the layer uniformity. The considerations derived from the planetary multiwafer reactors leading to the new reactor design are presented and the experimental results are discussed. Also it could be demonstrated, that all processes from the AIX 200 reactors can be easily transferred to this new AIX 200/4 reactor. >

A new adaptive fault tolerant method recently proposed utilizes the natural adaptation of the 1-D least mean square (LMS) adaptive filter to compensate for certain types of hardware failures. In this paper, the method is extended to the 2-D LMS filter to produce the 2-D fault tolerant LMS (FTLMS) algorithm. The results of the implementation are then demonstrated through example.

Several recent publications have developed the concept of adaptive fault tolerance (AFT) by demonstrating how adaptive filter architectures and adaptive algorithms can be designed to continue operating effectively in the presence of certain classes of hardware failures. Previous studies limited the use of AFT to one-dimensional FIR filter structures. This paper further develops the concept of AFT for one-dimensional IIR filter structures, demonstrating that indeed AFT can be extended to these more general classes of linear systems.

To satisfy the demand for material film structures for the fabrication of blue and green light emitting diodes and lasers, we developed metalorganic chemical vapor deposition (MOCVD) reactors for various batch sizes. All these reactors are capable of depositing GaInAlN material films. For the growth of single crystalline semiconductor films with a large band gap, process temperatures in excess of 1000/spl deg/C are required. Such temperatures have not been encountered in MOCVD for optoelectronic films before. Consideration of the nature of the MOCVD process forced a thermal optimization of the reactors in order to prevent unstable chemical compounds-in particular the precursors trimethylindium and tri(m)ethylgallium from suffering premature decomposition. The grown materials were characterized using photoluminescence mapping, spectrometry and sheet resistivity measurements.

The optimization of growth parameters for uniform deposition of GaInAs(P) compounds on InP has been topic of many reactor design studies up to the present. In most cases geometrical design provided optimization for only one of the compositional spectrum range of the Ga-In-As-P material family. The approaches were to compensate thermal distribution nonuniformities on the susceptors. These particularly cause compositional nonuniformities related to the temperature dependence in Ga/In or As/P distribution coefficients. This study was performed to get insight into the kinetic and transport processes in MOVPE reactors to have a general improvement for the entire material group of the InP based compound materials. >

A new MOVPE reactor is described which allows cost effective manufacturing of GaAs/Ge solar cells. The reactor, which has a batch size in excess of 0.25 m/sup 2/, was co-developed by Spectrolab and Aixtron Semiconductor Technologies over a two year time frame and was installed at Spectrolab in late 1993. Manufacturing readiness data on large area single junction GaAs/Ge solar cells show that the thickness and compositional uniformity of GaAs and AlGaAs layers grown in the system are /spl plusmn/3%, and /spl plusmn/1.5% respectively. There is excellent correlation between empirical data and simulations performed during the initial reactor development phase. The minimum average AM0, 28/spl deg/C efficiencies of 7 mil and 5.5 mil single junction GaAs/Ge solar cells, manufactured from material grown on this system, are over 18.5%.

Results of DC characteristic and RF power performance measurements on depletion mode InGaAs MISFETs with submicron gate lengths fabricated using an epitaxial process are presented. At 18 GHz, an output power density of 0.92 W/mm was obtained at an input power of 19.5 dBm. The corresponding gain and power-added efficiency were 3.2 dB and 29% respectively. The highest power-added efficiency obtained was 32% with a corresponding power gain and output power density of 4.3 dB and 0.86 W/mm, respectively, at an input power of 18 dBm. At 20 GHz, an output power density of 0.79 W/mm was obtained with a corresponding gain and power-added efficiency of 3.0 dB and 23%, respectively. The highest power-added efficiency was 25% at 0.73 W/mm output power density and 4.8 dB gain. >

We describe the use of a family of high temperature MOVPE reactors to grow SiC and III-V nitrides such as GaN. The load capacity ranges from single wafer machines to multiple wafer mass production reactors. All of these reactors have a two flow injection system, allowing separated inlet of the various reactants. To achieve maximum growth uniformity, the Gas Foil Rotation/sup R/ principle is applied. The multiwafer reactors are planetary reactors with a double rotation of substrates. Extensive modeling has been used in order to find the optimum reactor geometries. An optimization of uniformity and efficiency and a minimization of undesired parasitic reactions has thus been obtained.

An algorithm-based fault tolerant method termed the fault tolerant least-mean-squares (FTLMS) algorithm is extended from 1-D to 2-D. The algorithm enables the LMS to correct for a particular type of weight update failure called a stuck-at fault. The key to the algorithm is an overcomplete set of vectors used to transform the input. In developing the 2-D version, the properties of performance-enhancing transforms are investigated, leading to a transform structure that gives the algorithm a more desirable convergence rate. Various transforms are evaluated according to their reduction in eigenvalue ratio (EVR) for stationary inputs.

Since the invention of the Planetary Reactors(R) a reliable tool for mass production of various III-V compounds is existing. These reactors haven proven to grow extremely uniform films together with a highly efficient utilization of the precursors. Now a new generation of Planetary Reactors(R) is introduced: the so-called G3 systems. Their main features are: an inductive heating system with extremely low thermal mass for precise and fast heating, high flexibility in the reactor size (15/spl times/2", 35/spl times/2" to 9/spl times/4" wafer load so far, further enlargement possible) and the option to use a fully automated cassette-to-cassette wafer loading system. The benefits of this new design are very short cycle times, extreme run-to-run stability and even further reduced cost of ownership. The performance of this reactor will be discussed in conjunction with the well established ATX 2400 reactor with a set up of 15/spl times/2" or 5/spl times/4" wafer. Uniformity of thickness, luminescence intensity and composition of the most important III-V compounds such as GaInP, GaInAsP and AlGaInP were shown.

Although many research institutions presently are using single wafer reactors for the growth of III-V nitrides, there is already a strong request for mass production MOCVD systems. With the planetary reactors a reactor type exists which already meets all requirements of blue LED and laser mass production. We present results on the growth of GaInAlN films in multiwafer planetary reactors with 7/spl times/2" wafer capacity.

In gain-coupled (GC) distributed-feedback (DFB) lasers of absorptive grating type, the device characteristics depend very much on the absorptive grating configuration such as duty cycle, layer thickness, conduction type, and material composition. We have fabricated 1.55 /spl mu/m InGaAsP/InP strained multiple quantum well (MQW) DFB lasers having different absorptive grating thickness and different conduction type. Lasing characteristics of these lasers were compared with regard to coupling coefficients and absorption saturation. Through net gain measurement, information useful for designing and optimizing the absorptive grating was obtained.

The purpose of the experiments presented in this paper is to study the effects of intentional oxygen and silicon doping on the properties of GaN layers. We will report for the first time on the comparison of these dopants and the doping of GaN with oxygen using N/sub 2/O.

Further improvement of thickness and compositional homogeneity was sought in order to increase the usable wafer area for sophisticated device production and thus reduce the manufacturing costs in low-pressure metalorganic vapor-phase epitaxy processes. The gas-foil concept for wafer rotation was used to achieve these goals. In this technique the substrate is placed on a graphite carrier floating on a gas foil (high-purity H/sub 2/). The same gas flow also forces the carrier to rotate. The thickness uniformities of InP, GaInAs and GaInAsP layers grown with the gas-foil rotation susceptor in a single-wafer reactor were better than +or-1.5%. The variation of lattice mismatch of ternary and quaternary layers was below 2.5*10/sup -4/. The GaInAsP wavelength variation was smaller than 4 nm over the entire wafer area (a rim of 5 mm excluded). >