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Materials Science, Engineering, and Commercialization
Department of Physics
Ph.D. Physics, Viginia Tech, Blacksburg Virginia (1987)
BS Physics, Bradley University, Peoria, Illinois (1980)
Welcome to the Holtz Laboratory website! Our optics research group at Texas State University focuses on understanding fundamental and applied properties of semiconductors. Of particular interest are the III-nitrides, which have applications including high-power transistors, light-emitting and laser diodes, and photovoltaics. We study the underlying physics related to optical and vibrational properties of nitride semiconductors, which are the foundation of these applications. We use our optics knowledge to carry out applied materials research for device design and processing issues, such as abating self-heating in high-power electronics and photonics.
If you enjoy fundamental physics and hands-on experimental science, and care about the practical application of your work, this research is for you!
Mark Holtz is an experimental physicist working in nanoscale materials, particularly on questions relating to group III-nitride semiconductors, device design and processing, device self-heating, and thermal properties. He has been involved in condensed matter physics research since 1984. Prior to arriving at Texas State University in 2013, Dr. Holtz was Professor of Physics at Texas Tech University (1991-2013).
Dr. Holtz has published over 125 peer-reviewed journal articles along with numerous conference proceedings. He has received over $4.5M in external funding on grants and contracts totaling in excess of $15.8M from federal, state, and private agencies. He has advised and co-advised ten PhD students, over 50 MS students, and postdoctoral researchers, all of whom are working in industry or academia.
Texas Tech University (1991-2013 professor)
Max Planck Institut FKF (1987-1989 postdoc)
Michigan State University (1989-1991 visiting scholar)
Texas Instruments (1998 sabbatical)
Intel (1997 summer)
A principal interest in Dr. Holtz’ research is the study of optical properties of group-III-nitride semiconductors. Our work concerns both fundamental optical and vibrational processes in these materials and applications to the relationship between growth approach, micro- and nano-scale structure, and material properties. We use photoluminescence (spectroscopy and time-resolved emission) to examine optical transitions and the effects of temperature, pressure and stress on these processes. Understanding and accounting for these effects is critical for device design and performance. Visible and UV micro-Raman spectroscopy studies enable understanding of fundamental phonon processes, as well as the effects of stress and heating in device structures, which influence operating characteristics and can be a leading failure mechanism. [1-8]
Applied studies have been aimed at process development, such as plasma etching and device operation of semiconductor devices such as the heterojunction field-effect transistor based on GaN. We are specifically interested in the self-heating mechanisms of these devices, which degrades conductance and can eventually lead to device failure. To understand this failure mechanism, we developed UV Raman measurements as a way to determine temperature rise in the two-dimensional electron gas (2DEG) of these interesting structures. [9-12]
Research in thermal properties has led to innovative studies of the thermal conductivity of thin films and nanowires. In this work, the combination of simulation and systematic studies of device design have proven to be key partners in extracting meaningful results. In our study of supported aluminum nanowires, we observed the thermal conductivity to drop dramatically as size decreases. This drop in thermal conductivity results from parasitic losses to the substrate, which could only be fully understood through simulations tightly coupled to the experiments. [13-15]