Condensed Matter Physics

Welcome to the Semiconductor Optoelectronics research group. The research area of our group includes investigating Interactions of Radiations with Matter (IRML) especially optoelectronic devices (having various architectures and material compositions) and with soft diagnostic mediums, especially with body fluids. Our present focus is on developing various types of infrared detectors with applications for improving the security and quality of life of our communities.

In particular, our work focuses on the various architecture and material composition of quantum (or, hetero-junction) semiconductor structures of infrared detectors by exploring necessary physics, theory and modeling paralleled by the experimental verification. Utilizing IR interaction with various types of infrared detectors we explore inter-sub band and inter-valence band transition processes in Quantum Rings and Dots, Dot in well (DWELL), and in wires and heterojunction structures. Our patented split-off detectors provide extended thresholds without an increase in the dark current, thus operating at higher temperatures, which avoids cryogenic cooling. This not only reduces the cost and weight, but also simplifies the infrared detector systems allowing widespread usage. The idea of incorporating a graded-barrier structure with an offset, resulted in a recent patent on hot carrier detectors where the threshold wavelength was extended beyond the standard spectral limit given by the relationship λ_c = hc/Δ, where λ_c is cutoff wavelength and Δ the activation energy (or bandgap) of the semiconductor structure (or material). Using QD structures can lead to a longer lifetime of carriers, which will enhance the device performance. We have a comprehensive approach for their characterization and several projects were funded by the U.S. Army Research Office (ARO), National Science Foundation (NSF), Georgia Research Alliance (GRA) and U.S. Air Force. Our current projects also include novel nanoplasmonic ideas to enhance the performance of our devices and understand optical characteristics of graphine and other quantum materials to select the appropriate material combinations for novel architectures.

Detector Structure

Maximized response observed at certain bias voltages

Typical normalized IR spectra of biological medium

Schematic of measurement and data analysis tool

Our group also pursue identifying IR spectral markers for disease induced changes within the constituents of body fluids that is relevant for earlier detection of various health conditions like inflammatory bowel diseases (IBD) and various cancers. In this regard, we have demonstrated this technique using serum samples of experimental mouse models of Ulcerative colitis and cancers (melanoma and Lymphoma) and are in the process of applying to human serum samples. The success of this project and the understanding of these changes in spectral markers are relevant to the mission of improving people’s health and quality of life. Aiding in early detection and diagnosis of disease with a cost-effective way to enhance the compliance rate for disease screening could ultimately enhance society’s ability to combat debilitating and costly chronic diseases such as Inflammatory Bowel Diseases (IBDs) and cancer. Our study also directed towards designing and developing a prototype of a portable tool for facilitating such measurements. In this regard, we have studied the possible use of commercially available small Fourier transform Infrared (FTIR) spectrometer with single reflection attenuated total reflectance (ATR) unit, integrated with the fully automated spectral measurements and analysis software package.

Faculty: A. G. Unil Perera