Academic Achievement of National Social Fraternity Pledges Compared to Non-Fraternity Students (open access)

Academic Achievement of National Social Fraternity Pledges Compared to Non-Fraternity Students

This study examined the academic achievement of national social fraternity pledges compared to non-fraternity students at the University of Texas at Arlington. It was done to determine whether significant differences existed between the grade point averages of pledges of social fraternities and those of students who did not pledge a social fraternity, and to determine whether significant differences existed among fraternities when compared with each other with respect to academic achievement. This study was meant to provide a research design that could be used by other colleges and universities with fraternities to conduct the same comparison of academic performance. In the fall semester of 1989, 164 pledges were selected as the population for the study to be matched with non-fraternity students based on Scholastic Aptitude Test (SAT) scores, age, sex, classification, academic major, and number of hours attempted. A T-test of like groups was performed on the entire population with no significant difference found at the .05 level between all the fraternity pledges and all the matched pairs. A T-test of like groups was performed on the pledges from each separate organization and there was a significant difference among three of the fraternities. Two of the fraternities had significantly higher …
Date: August 1990
Creator: Gardner, Kent Lee
System: The UNT Digital Library
A Descriptive Study of Statewide Bibliographic Databases (open access)

A Descriptive Study of Statewide Bibliographic Databases

This dissertation has compiled information about statewide bibliographic databases, their format, their cost, the number of titles and records, how they are being used, what kinds of libraries are using such databases in each state, and the effectiveness of those databases. General information about twenty-eight states' bibliographic databases is included in this dissertation. The users of thirteen states responded to a questionnaire, surveying the effectiveness of the statewide database in their state. The costs to the individual states varies from zero, where all costs are covered by local funds or Library Services and Construction Act fund, up to 4.4 million dollars. Usage of interlibrary loan increase is detailed and explained. There has never been an evaluation of the effectiveness of a statewide bibliographic database. This is a descriptive study of statewide bibliographic databases. No other such study appears in library and information sciences indexes.
Date: August 1992
Creator: Gardner, Stan (Stan A.)
System: The UNT Digital Library
Forest Landscape Dynamics: a Semi-Markov Modeling Approach (open access)

Forest Landscape Dynamics: a Semi-Markov Modeling Approach

A transition model (MOSAIC) is used to describe forest dynamics at the landscape scale. The model uses a semi-Markov framework by considering transition probabilities and Erlang distributed holding times in each transition. Parameters for the transition model are derived from a gap model (ZELIG). This procedure ensures conceptual consistency of the landscape model with the fine scale ecological detail represented by the forest gap model. Spatial heterogeneity in the transition model is driven by maps of terrain with characteristics contained in a Geographic Information System (GIS) database. The results of the transition model simulations, percent cover forest type maps, are exported to grid-maps in the GIS. These cover type maps can be classified and used to describe forest dynamics using landscape statistics metrics. The linkage model-GIS enhances the transition model spatial analytical capabilities. A parameterization algorithm was developed that takes as input gap model tracer files which contain the percent occupation of each cover type through time. As output, the algorithm produces a file that contains the parameter values needed for MOSAIC for each one of the possible transitions. Parameters for the holding time distribution were found by calculating an empirical estimate of the cumulative probability function and using a …
Date: August 1997
Creator: Ablan, Magdiel
System: The UNT Digital Library
An examination of performance aspects of two major works for percussion ensemble: Toccata by Carlos Chávez and Cantata para América mágica by Alberto Ginastera, a lecture recital, together with four recitals of selected works of I. Stravinsky, R. Vaughan Williams, W.A. Mozart, V. Persichetti, and P. Hindemith (open access)

An examination of performance aspects of two major works for percussion ensemble: Toccata by Carlos Chávez and Cantata para América mágica by Alberto Ginastera, a lecture recital, together with four recitals of selected works of I. Stravinsky, R. Vaughan Williams, W.A. Mozart, V. Persichetti, and P. Hindemith

This study addresses the ways and means a conductor may approach two major twentieth century works written specifically for percussion ensemble. Performance techniques and decisions on aesthetics made by the conductor in dealing with such items as timbre, balance, pitch levels, and pitch relationships are also considered.
Date: August 1991
Creator: George, Matthew
System: The UNT Digital Library
Spectral analysis of the turbulent mixing of two fluids (open access)

Spectral analysis of the turbulent mixing of two fluids

We describe a spectral approach to the investigation of fluid instability, generalized turbulence, and the interpenetration of fluids across an interface. The Technique also applies to a single fluid with large variations in density. Departures of fluctuating velocity components from the local mean are far subsonic, but the mean Mach number can be large. Validity of the description is demonstrated by comparisons with experiments on turbulent mixing due to the late stages of Rayleigh-Taylor instability, when the dynamics become approximately self-similar in response to a constant body force. Generic forms for anisotropic spectral structure are described and used as a basis for deriving spectrally integrated moment equations that can be incorporated into computer codes for scientific and engineering analyses.
Date: September 1995
Creator: Steinkamp, M. J.
System: The UNT Digital Library
Inertial fusion energy: A clearer view of the environmental and safety perspectives (open access)

Inertial fusion energy: A clearer view of the environmental and safety perspectives

If fusion energy is to achieve its full potential for safety and environmental (S&E) advantages, the S&E characteristics of fusion power plant designs must be quantified and understood, and the resulting insights must be embodied in the ongoing process of development of fusion energy. As part of this task, the present work compares S&E characteristics of five inertial and two magnetic fusion power plant designs. For each design, a set of radiological hazard indices has been calculated with a system of computer codes and data libraries assembled for this purpose. These indices quantify the radiological hazards associated with the operation of fusion power plants with respect to three classes of hazard: accidents, occupational exposure, and waste disposal. The three classes of hazard have been qualitatively integrated to rank the best and worst fusion power plant designs with respect to S&E characteristics. From these rankings, the specific designs, and other S&E trends, design features that result in S&E advantages have been identified. Additionally, key areas for future fusion research have been identified. Specific experiments needed include the investigation of elemental release rates (expanded to include many more materials) and the verification of sequential charged-particle reactions. Improvements to the calculational methodology are …
Date: November 1, 1996
Creator: Latkowski, J.F.
System: The UNT Digital Library
A Compton camera for spectroscopic imaging from 100 keV to 1 MeV (open access)

A Compton camera for spectroscopic imaging from 100 keV to 1 MeV

A review of spectroscopic imaging issues, applications, and technology is presented. Compton cameras based on solid state semiconductor detectors stands out as the best system for the nondestructive assay of special nuclear materials. A camera for this application has been designed based on an efficient specific purpose Monte Carlo code developed for this project. Preliminary experiments have been performed which demonstrate the validity of the Compton camera concept and the accuracy of the code. Based on these results, a portable prototype system is in development. Proposed future work is addressed.
Date: December 31, 1998
Creator: Earnhart, J. R. D.
System: The UNT Digital Library
Scaling supernova hydrodynamics to the laboratory (open access)

Scaling supernova hydrodynamics to the laboratory

Supernova (SN) 1987A focused attention on the critical role of hydrodynamic instabilities in the evolution of supernovae. To test the modeling of these instabilities, we are developing laboratory experiments of hydrodynamic mixing under conditions relevant to supernovae. Initial results were reported in J. Kane et al., Astrophys. J.478, L75 (1997) The Nova laser is used to shock two-layer targets, producing Richtmyer-Meshkov (RM) and Rayleigh-Taylor (RT) instabilities at the interfaces between the layers, analogous to instabilities seen at the interfaces of SN 1987A. Because the hydrodynamics in the laser experiments at intermediate times (3-40 ns) and in SN 1987A at intermediate times (5 s-10{sup 4} s) are well described by the Euler equations, the hydrodynamics scale between the two regimes. The experiments are modeled using the hydrodynamics codes HYADES and CALE, and the supernova code PROMETHEUS, thus serving as a benchmark for PROMETHEUS. Results of the experiments and simulations are presented. Analysis of the spike and bubble velocities in the experiment using potential flow theory and a modified Ott thin shell theory is presented. A numerical study of 2D vs. 3D differences in instability growth at the O-He and He-H interface of SN 1987A, and the design for analogous laser experiments …
Date: June 1, 1999
Creator: Kane, J.O.
System: The UNT Digital Library
A Comparison of Middle Aged and College Aged Adults' Perceptions of Elder Abuse (open access)

A Comparison of Middle Aged and College Aged Adults' Perceptions of Elder Abuse

The purpose of this study was to examine the impact of (a) respondent age, (b) age and gender of perpetrator and victim, and (c) history of experienced violence on perceptions of elder abuse. Two-hundred and one (N = 201) middle-aged adults and 422 college students were assessed. Measures included adaptations of the Severity of Violence Against Women Scale and Elder Abuse Attitudes and Behavioral Intentions Scale-Revised. Middle-aged respondents viewed psychological behaviors more harshly than young. Middle-aged females and young males were less tolerant of middle-aged perpetrators. While past performance of elder abuse was predictive of future elder abuse, history of childhood abuse was not. Exploratory analyses examined middle-aged respondents' judgments of abusive behaviors and perceptions based on age of perpetrator. Middle-aged and young adults' willingness to respond to dimensions of quality, severity, and reportability were also examined.
Date: August 1994
Creator: Childs, Helen W. (Helen Warren)
System: The UNT Digital Library
An Evaluation of Unsaturated Flow Models in an Arid Climate (open access)

An Evaluation of Unsaturated Flow Models in an Arid Climate

The objective of this study was to evaluate the effectiveness of two unsaturated flow models in arid regions. The area selected for the study was the Area 5 Radioactive Waste Management Site (RWMS) at the Nevada Test Site in Nye County, Nevada. The two models selected for this evaluation were HYDRUS-1D [Simunek et al., 1998] and the SHAW model [Flerchinger and Saxton, 1989]. Approximately 5 years of soil-water and atmospheric data collected from an instrumented weighing lysimeter site near the RWMS were used for building the models with actual initial and boundary conditions representative of the site. Physical processes affecting the site and model performance were explored. Model performance was based on a detailed sensitivity analysis and ultimately on storage comparisons. During the process of developing descriptive model input, procedures for converting hydraulic parameters for each model were explored. In addition, the compilation of atmospheric data collected at the site became a useful tool for developing predictive functions for future studies. The final model results were used to evaluate the capacities of the HYDRUS and SHAW models for predicting soil-moisture movement and variable surface phenomena for bare soil conditions in the arid vadose zone. The development of calibrated models along …
Date: December 1, 1999
Creator: Dixon, J.
System: The UNT Digital Library
Solution based temperature of Perovskite-type oxide films and powders (open access)

Solution based temperature of Perovskite-type oxide films and powders

Conventional solid state reactions are diffusion limited processes that require high temperatures and long reaction times to reach completion. In this work, several solution based methods were utilized to circumvent this diffusion limited reaction and achieve product formation at lower temperatures. The solution methods studied all have the common goal of trapping the homogeneity inherent in a solution and transferring this homogeneity to the solid state, thereby creating a solid atomic mixture of reactants. These atomic mixtures can yield solid state products through {open_quotes}diffusionless{close_quotes} mechanisms. The effectiveness of atomic mixtures in solid state synthesis was tested on three classes of materials, varying in complexity. A procedure was invented for obtaining the highly water soluble salt, titanyl nitrate, TiO(NO{sub 3}){sub 2}, in crystalline form, which allowed the production of titanate materials by freeze drying. The freeze drying procedures yielded phase pure, nanocrystalline BaTiO{sub 3} and the complete SYNROC-B phase assemblage after ten minute heat treatments at 600{degrees}C and 1100{degrees}C, respectively. Two novel methods were developed for the solution based synthesis of Ba{sub 2}YCu{sub 3}O{sub 7-x} and Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10}. Thin and thick films of Ba{sub 2}YCu{sub 3}O{sub 7-x} and Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} were synthesized by …
Date: April 1, 1995
Creator: McHale, J.M. Jr.
System: The UNT Digital Library
Solution based synthesis of perovskite-type oxide films and powders (open access)

Solution based synthesis of perovskite-type oxide films and powders

Conventional solid state reactions are diffusion limited processes that require high temperatures and long reaction times to reach completion. In this work, several solution based methods were utilized to circumvent this diffusion limited reaction and achieve product formation at lower temperatures. The solution methods studied all have the common goal of trapping the homogeneity inherent in a solution and transferring this homogeneity to the solid state, thereby creating a solid atomic mixture of reactants. These atomic mixtures can yield solid state products through diffusionless mechanisms. The effectiveness of atomic mixtures in solid state synthesis was tested on three classes of materials, varying in complexity. A procedure was invented for obtaining the highly water soluble salt, titanyl nitrate, TiO(NO{sub 3}){sub 2}, in crystalline form, which allowed the production of titanate materials by freeze drying. The freeze drying procedures yielded phase pure, nanocrystalline BaTiO{sub 3} and the complete SYNROC-B phase assemblage after ten minute heat treatments at 600 C and 1,100 C, respectively. Two novel methods were developed for the solution based synthesis of Ba{sub 2}YCu{sub 3}O{sub 7{minus}x} and Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10}. Thin and thick films of Ba{sub 2}YCu{sub 3}O{sub 7{minus}x} and Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} were …
Date: January 1, 1995
Creator: McHale, J. M. Jr.
System: The UNT Digital Library
Information Management in Local Area Networks: Impact on Users' Perceptions (open access)

Information Management in Local Area Networks: Impact on Users' Perceptions

In this study, computer human interaction factors are examined as a possible source of information to aid in the operation and management of local area computer networks. Users' perceptions of computer performance and response time are evaluated in relation to specific modifications in the information organization of a file server in a local area network configuration running in Novell 3.11.
Date: May 1994
Creator: Norton, Melanie J.
System: The UNT Digital Library
Should Corrective Feedback Come Before or After Responding to Establish a "New" Behavior? (open access)

Should Corrective Feedback Come Before or After Responding to Establish a "New" Behavior?

The purpose of this study was to determine the optimal form and timing of feedback to establish a "new" behavior. It examined the relative effectiveness of delivering a corrective feedback immediately before the learner responds to a previously incorrect trial as compared to delivering a corrective feedback immediately after the incorrect response is made. Corrective feedback delivered immediately before the next opportunity to respond produced better learning than corrective feedback delivered immediately after a response. The Feedback Before condition decreased errors during training and increased acquisition rates. Results also indicated an interaction between time of feedback delivery and the complexity of the task. As the task complexity increased, the results were more dramatic in favor of the Feedback Before condition.
Date: December 1997
Creator: Roberts, Pamela J.
System: The UNT Digital Library
Mistrust, Type of Problem, Counselor Ethnicity, Counselor Preference, and Expectations toward Counseling among Black Students (open access)

Mistrust, Type of Problem, Counselor Ethnicity, Counselor Preference, and Expectations toward Counseling among Black Students

The purpose of this study was to explore relationships between and among the degree of mistrust black students hold towards Whites, the students' preferences for race of counselor, and the discussion of problems that are sexual in nature. Participants consisted of 60 black females and 51 black males recruited from a university population. All subjects completed the Terrell and Terrell Cultural Mistrust Inventory, Fischer-Turner Attitudes Toward Seeking Professional Psychological Help Scale, Corrigan and Schmidt Counselor Rating Form - Short Form, Tinsley Expectations About Counseling Inventory, and the Thermometer Method Form developed specifically for this project. A multiple regression model was used to explore the hypotheses of this study. The criterion variables consisted of scores on the Expectations About Counseling Form and Counselor Rating Form. Analyses revealed that the most significant predictors of counseling expectations were race of counselor and participant gender. Black students who were asked to assume \ they would see a black counselor had more favorable expectations about counseling than those black students asked to assume they would see a white counselor. Female participants had more favorable expectations about counseling than male participants. Results also indicated that the most significant predictors of counselor ratings were race of counselor …
Date: August 1992
Creator: Nickerson, Kim J. (Kim Jung)
System: The UNT Digital Library
Comparison of Visual and Auditory Continuous Performance Tests in Adults (open access)

Comparison of Visual and Auditory Continuous Performance Tests in Adults

Two continuous performance tests were administered to normal adult subjects. The mode of presentation (visual or auditory) and the type of task (vigilance or distractibility) were varied, and their effects on performance measured. Data were collected on eighty-two subjects, and results indicated that auditory presentation of stimuli increased the difficulty of both tasks. Results also suggest that the distractibility task administered in either mode was more difficult than the vigilance task. Intercorrelations among the four continuous performance tasks are provided. Normative data are presented on all four tasks administered. A measure of symptoms of attention-deficit disorder in adults, the Adult Behavior Checklist, was found to correlate significantly with another measure of pathology, the SCL-90-R.
Date: December 1993
Creator: Taylor, Cindy J.
System: The UNT Digital Library
The Effects of Music Training on Electroencephalographic Coherence of Preschool Children (open access)

The Effects of Music Training on Electroencephalographic Coherence of Preschool Children

The purpose of this study was to examine the effects of music training on electroencephalographic (EEG) coherence of preschool children. EEG coherence is a measurement of brain wave activity that reflects anatomical and neurophysiological parameters and functional connectivity between areas of the brain. Participants were 4- to 6-year-old children divided into two groups: one received music training for 20 minutes twice a week for 10 weeks while the other group served as controls. Nineteen channels of EEG data were collected from each child pre- and post-training. Data were collected from three conditions: eyes-open resting, listening to music, and performing the Object Assembly subtest of the Weschler Preschool and Primary Scale of Intelligence - Revised (1989). The hypothesis was that the music training group would show increased EEG coherence as compared to controls. The EEG data was reduced into seven bandwidths and analyzed separately for each condition. Multiple ANCOVAs were used to factor out pre-test variability and to maximize connectivity changes between the two groups. The dependent measures were the post-QEEG electrode pairs and the covariates were the pre-QEEG electrode pairs. Results indicated the eyes-open and listening to music conditions showed more significant changes between the groups than the Object Assembly …
Date: August 1999
Creator: DeBeus, Roger J. (Roger John)
System: The UNT Digital Library
Study of radicals, clusters and transition state species by anion photoelectron spectroscopy (open access)

Study of radicals, clusters and transition state species by anion photoelectron spectroscopy

Free radicals, elemental and van der Waals clusters and transition state species for bimolecular chemical reactions are investigated using anion photoelectron spectroscopy. Several low-lying electronic states of ozone have been identified via photoelectron spectroscopy of O{sub 3}{sup {minus}}. A characterization of these states is important to models for atmospheric ozone reaction kinetics. The fluoroformyloxyl radical, FCO{sub 2}, has been investigated, providing vibrational frequencies and energies for two electronic states. The technique has also been employed to make the first direct observation and characterization of the NNO{sub 2} molecule. Several electronic states are observed for this species which is believed to play a role as a reactive intermediate in the N + NO{sub 2} reaction. The experimental results for all three of these radicals are supplemented by ab initio investigations of their molecular properties. The clusters investigations include studies of elemental carbon clusters (C{sub 2}{sup {minus}} {minus} C{sub 11}{sup {minus}}), and van der Waals clusters (X{sup {minus}}(CO{sub 2}){sub n}, X = I, Br, Cl; n {le} 13 and I{sup {minus}} (N{sub 2}O){sub n=1--11}). Primarily linear clusters are observed for the smaller carbon clusters, while the spectra of the larger clusters contain contribution from cyclic anion photodetachment. Very interesting ion-solvent interactions are …
Date: August 1, 1994
Creator: Arnold, D. W.
System: The UNT Digital Library
Filial Therapy with Native Americans on the Flathead Reservation (open access)

Filial Therapy with Native Americans on the Flathead Reservation

This study was designed to determine the effectiveness of the 10-week filial therapy model as an intervention for Native American parents and their children residing on the Flathead Reservation in Montana. Filial therapy is an approach used by play therapists to train parents to be therapeutic agents with their own children. Parents are taught basic child-centered play therapy skills and practice those skills during weekly play sessions with their children. The purpose of this study was to determine if filial therapy is effective in: 1) increasing parental acceptance of Native Americans residing on the Flathead Reservation of their children; 2) reducing the stress level of those parents; 3) improving empathic behaviors of those parents toward their children; 4) changing the play behaviors of children with their parents who participated in the training; and, 5) enhancing the self-concept of those children. The experimental group parents (N=11) received 10 weekly 2-hour filial therapy training sessions and participated in weekly 30-minute play sessions with one of their children. The control group (N=10) received no treatment during the 10 weeks. All adult participants completed the Porter Parental Acceptance Scale and the Parenting Stress Index. Child participants completed the Joseph Pre-school and Primary Self Concept …
Date: May 1996
Creator: Glover, Geraldine J.
System: The UNT Digital Library
A Next-to-Leading-Order QCD Analysis of Neutrino-Iron Structure Functions at the Tevatron (open access)

A Next-to-Leading-Order QCD Analysis of Neutrino-Iron Structure Functions at the Tevatron

Nucleon structure functions measured in neutrino-iron and antineutrino-iron charged-current interactions are presented. The data were taken in two high-energy high-statistics runs by the LAB-E detector at the Fermilab Tevatron. Structure functions are extracted from a sample of 950,000 neutrino and 170,000 antineutrino events with neutrino energies from 30 to 360 GeV. The structure functions F{sub 2} and xF{sub 3} are compared with the predictions of perturbative Quantum Chromodynamics (PQCD). The combined non-singlet and singlet evolution in the context of PQCD gives value of {Lambda}NLO,(4)/MS = 337 {+-} 28 (exp.) MeV, which corresponds to {alpha}{sub S}(M{sub Z}{sup 2}) = 0.119 {+-} 0.002 (exp.) {+-} 0.004 (theory), and with a gluon distribution given by xG(x,Q{sub 0}{sup 2} = 5GeV{sup 2}) = (2.22 {+-} 0.34) {times} (1 {minus} x){sup 4.65{+-}0.68}.
Date: June 1, 1997
Creator: Seligman, W. G.
System: The UNT Digital Library
A Compton scatter camera for spectral imaging of 0.5 to 3.0 MeV gamma rays (open access)

A Compton scatter camera for spectral imaging of 0.5 to 3.0 MeV gamma rays

A prototype Compton scatter camera for imaging gamma rays has been built and tested. This camera addresses unique aspects of gamma-ray imaging at nuclear industrial sites, including gamma-ray energies in the 0.5 to 3.0 MeV range and polychromatic fields. Analytic models of camera efficiency, resolution and contaminating events are developed. The response of the camera bears strong similarity to emission computed tomography devices used in nuclear medicine. A direct Fourier based algorithm is developed to reconstruct two-dimensional images of measured gamma-ray fields. Iterative ART and MLE algorithms are also investigated. The point response of the camera to gamma rays of energies from 0.5 to 2.8 MeV is measured and compared to the analytic models. The direct reconstruction algorithm is at least ten times more efficient than the iterative algorithms are also investigated. The point response of the camera to gamma rays energies from 0.5 to 2.8 MeV is measured and compared to the analytic models. The direct reconstruction algorithm is at least ten times more efficient than the iterative algorithms and produces images that are, in general, of the same quality. Measured images of several phantoms are shown. Important results include angular resolutions as low as 4.4{degrees}, reproduction of phantom …
Date: December 31, 1994
Creator: Martin, J.B.
System: The UNT Digital Library
Development and Validation of the Checklist for Differential Diagnosis of Attentional Problems (open access)

Development and Validation of the Checklist for Differential Diagnosis of Attentional Problems

The current study discussed the development and validation of the Checklist for Differential Diagnosis of Attentional Problems (CDDAP), a tool for use with adults seeking diagnosis and treatment of an Attention Deficit Hyperactivity Disorder. Normative data are provided on three subject groups (ADHD adults, controls, and adults with other psychiatric disorders). Convergent validity was established with the SCL-90, and criterion validity established through comparing scaled scores with final diagnoses. Overall, this measure was accurate at differentiating adults with ADHD from controls and adults with other psychiatric disorders. Results indicated that the CDDAP was also able to identify other psychiatric disorders with 71 to 92% accuracy, depending on the disorder.
Date: May 1999
Creator: Taylor, Cindy J.
System: The UNT Digital Library
The Relationship Between Hostility and Social Support with Chronic Pain and Health Indicators (open access)

The Relationship Between Hostility and Social Support with Chronic Pain and Health Indicators

The purposes of the study were to examine the psychosocial variables of hostility and social support, and their independent relationships with resting physiological levels and chronic pain symptoms, and to examine the independent relationships of chronic pain chronicity and social support with hostility.
Date: December 1997
Creator: Witham, Kevin J.
System: The UNT Digital Library
Carbon doping of III-V compound semiconductors (open access)

Carbon doping of III-V compound semiconductors

Focus of the study is C acceptor doping of GaAs, since C diffusion coefficient is at least one order of magnitude lower than that of other common p-type dopants in GaAs. C ion implantation results in a concentration of free holes in the valence band < 10% of that of the implanted C atoms for doses > 10{sup 14}/cm{sup 2}. Rutherford backscattering, electrical measurements, Raman spectroscopy, and Fourier transform infrared spectroscopy were amonth the techniques used. Ga co-implantation increased the C activation in two steps: first, the additional radiation damage creates vacant As sites that the implanted C can occupy, and second, it maintains the stoichiometry of the implanted layer, reducing the number of compensating native defects. In InP, the behavior of C was different from that in GaAs. C acts as n-type dopant in the In site; however, its incorporation by implantation was difficult to control; experiments using P co-implants were inconsistent. The lattice position of inactive C in GaAs in implanted and epitaxial layers is discussed; evidence for formation of C precipitates in GaAs and InP was found. Correlation of the results with literature on C doping in III-V semiconductors led to a phenomenological description of C in …
Date: September 1, 1994
Creator: Moll, A. J.
System: The UNT Digital Library