Mohammad Awwad

The Ohio State University

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Siddharth Rajan

The Ohio State University

Sheikh Ifatur Rahman

The Ohio State University

Zane Jamal-Eddine

The Ohio State University

Paul A. Fuerst

The Ohio State University

Dolena R. Ledee

University of Washington

Chandan Joishi

The Ohio State University

Diane R. Stothard

Eli Lilly (United States)

Thomas J. Byers

University of Bath

R. Armitage

Trimble (United States)

K.A.A. Sharshar

Egyptian Atomic Energy Authority

Cooperative Institutions

The Ohio State University

Sandia National Laboratories

University of California, Santa Barbara

United States Air Force Research Laboratory

Indian Institute of Technology Bombay

Indiana University – Purdue University Indianapolis

Indiana University School of Medicine

Centers for Disease Control and Prevention

University of Michigan–Ann Arbor

University of Utah

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Tunnel junction-enabled monolithically integrated GaN micro-light emitting transistor

Applied Physics Letters (2024)

Sheikh Ifatur Rahman Mohammad Awwad Chandan Joishi Zane Jamal-Eddine Brendan Gunning

GaN/InGaN microLEDs are a very promising technology for next-generation displays. Switching control transistors and their integration are key components in achieving high-performance, efficient displays. Monolithic integration of microLEDs with GaN switching devices provides an opportunity to control microLED output power with capacitive (voltage)-controlled rather than current-controlled schemes. This approach can greatly reduce system complexity for the driver circuit arrays while maintaining device opto-electronic performance. In this work, we demonstrate a 3-terminal GaN micro-light emitting transistor that combines a GaN/InGaN blue tunneling-based microLED with a GaN n-channel FET. The integrated device exhibits excellent gate control, drain current control, and optical emission control. This work provides a promising pathway for future monolithic integration of GaN FETs with microLED to enable fast switching, high-efficiency microLED display and communication systems.

10.1063/5.0213300

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The Evolutionary History of the Genus Acanthamoeba and the Identification of Eight New 18S rRNA Gene Sequence Types

Journal of Eukaryotic Microbiology (1998)

Diane R. Stothard Jill M. Schroeder‐Diedrich Mohammad Awwad Rebecca J. Gast Dolena R. Ledee

ABSTRACT The 18S rRNA gene ( Rns ) phylogeny of Acanthamoeba is being investigated as a basis for improvements in the nomenclature and taxonomy of the genus. We previously analyzed Rns sequences from 18 isolates from morphological groups 2 and 3 and found that they fell into four distinct evolutionary lineages we called sequence types T1‐T4. Here, we analyzed sequences from 53 isolates representing 16 species and including 35 new strains. Eight additional lineages (sequence types T5‐T12) were identified. Four of the 12 sequence types included strains from more than one nominal species. Thus, sequence types could be equated with species in some cases or with complexes of closely related species in others. The largest complex, sequence type T4, which contained six closely related nominal species, included 24 of 25 keratitis isolates. Rns sequence variation was insufficient for full phylogenetic resolution of branching orders within this complex, but the mixing of species observed at terminal nodes confirmed that traditional classification of isolates has been inconsistent. One solution to this problem would be to equate sequence types and single species. Alternatively, additional molecular information will be required to reliably differentiate species within the complexes. Three sequence types of morphological group 1 species represented the earliest divergence in the history of the genus and, based on their genetic distinctiveness, are candidates for reclassification as one or more novel genera.

Sequence (biology)

10.1111/j.1550-7408.1998.tb05068.x

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Design and Simulation of a III-Nitride Light Emitting Transistor

Semiconductor Science and Technology (2024)

Mohammad Awwad Sheikh Ifatur Rahman Chandan Joishi Joe F. McGlone Betty Lise Anderson

Abstract This paper describes the design and characteristics of monolithically integrated three-terminal gated III-Nitride light emitting diodes (LEDs) devices. The impact of channel doping and thickness on the voltage penalty of the transistor-LED hybrid device is analyzed, and it is shown that with appropriate design, low voltage drop can be realized across integrated gated LED structures. The impact of device design on the switching charge is investigated, and it is shown that the adoption of an integrated LED/transistor structure can reduce the switching charge necessary for operation of a switched LED display device by an order of magnitude when compared with stand-alone light-emitting diodes.

10.1088/1361-6641/ad7754

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Theoretical Analysis of Tunnel-Injected Sub-300 nm AlGaN Laser Diodes

IEEE Journal of Quantum Electronics (2020)

Riazul Arefin Weicheng You Sujit H. Ramachandra Syed M. N. Hasan Hyemin Jung

Electrically-pumped AlGaN-based edge-emitting laser diodes with a buried tunnel junction (TJ) for sub-300 nm emission are designed in this paper. Hole injection is one of the major concerns for the design of ultraviolet (UV) lasers based on this material system. The use of a low-resistive TJ as an intracavity contact within the devices will offer an opportunity to replace highly resistive p-type AlGaN-based cladding and contact layers by their n-doped counterparts. This advanced polarization-engineered interband TJs will lead to improved hole injection and a significantly reduced threshold voltage. The thermal properties of the tunnel-injected devices are thoroughly studied theoretically. For the demonstration of continuous-wave operating lasers, possible improvements in terms of better thermal management of the device are also discussed. Our improved design allows CW-operating AlGaN lasers with a threshold current density of <; 8 kA/cm ² and maximum optical output power of > 220 mW, yielding a wall-plug efficiency of > 2.8%.

Resistive touchscreen

Ultraviolet

10.1109/jqe.2020.3021404

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Simulation of GaN-based light emitting diodes incorporating composition fluctuation effects

Journal of Applied Physics (2022)

Sheikh Ifatur Rahman Zane Jamal-Eddine Zhanbo Xia Mohammad Awwad R. Armitage

III-Nitride light emitting diodes (LEDs) are widely used in a range of high efficiency lighting and display applications, which have enabled significant energy savings in the last decade. Despite the wide application of GaN LEDs, transport mechanisms across InGaN/GaN heterostructures in these devices are not well-explained. Fixed polarization sheet charges at InGaN/GaN interfaces lead to large interface dipole charges, which create large potential barriers to overcome. One-dimensional models for transport across such heterostructures predict turn-on voltages that are significantly higher than that found in real devices. As a result, conventional models for transport cannot predict the performance of new designs such as for longer wavelength LEDs, or for multi-quantum well LEDs. In this work, we show that incorporating low and high Indium compositions within quantum wells at the submicron scale can provide accurate prediction of the characteristics of GaN/InGaN light emitting diodes.

Wide-bandgap semiconductor

10.1063/5.0125684

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Annealing of Sputtered InSb Thin Film for III-V Semiconductor Devices Applications

International Conference on Aerospace Sciences and Aviation Technology (2017)

Mohammad Awwad Ahmed M. Hafez K.A.A. Sharshar

In this paper, the effect of annealing temperature on Indium antimonide (InSb) thin films has been studied.It is proved that the increase in annealing temperature enhances the crystallinity of the InSb thin film.Thin films of InSb have been deposited on silicon and glass substrates by RF sputtering, then vacuum-annealed at 150, 300, 390 and 450 ⁰C.Differential scanning calorimeter (DSC) analysis indicates that InSb thin film crystallizes at 389 ⁰C or above.X-ray diffraction (XRD) results show peaks at (111), ( 220) and ( 311) planes, which indicates the formation of crystalline grains.Fourier transform infrared (FTIR) spectroscopy indicates the decrease of optical transmittance upon increasing the annealing temperature, the analysis shows that InSb thin films have bandgaps between 0.233 and 0.241 e.v.

10.21608/asat.2017.22777

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Studies of the phylogeny, systematics and pathogenicity of Acanthamoeba using ribosomal and transfer RNA gene sequences

Thomas J. Byers Gregory C. Booton Diane R. Stothard Dolena R. Ledee Jill M. Schroeder

The use of ribosomal RNA gene sequences (rDNA) for the study of the phylogeny, systematics and pathogenicity of Acanthamoeba has been increasing steadily in recent years. Our laboratory has been actively involved in sequencing nuclear and mitochondria! rDNA in collaboration with investigators around the world. In progress to date, we have identified 12 discrete typing units (rDNA genotypes T1 to T12) which include 20 of 25 named species. The genotypes were revealed by phylogenetic analyses of nuclear 18S rDNA and mitochondrial 16S rDNA sequences. Six named species have distinctive genotypes. The rest of the species that have been examined belong to paraphyletic clusters, the largest of which is genotype T4. Mitochondrial tRNA sequence data have been used to further examine these clusters. Improved PCR and sequencing strategies using rDNA have been developed for genus-specific detection of Acanthamoeba and genotype identification of clinical and environmental isolates. Analysis of 61 strains isolated from Acanthamoeba keratitis indicate that 97% of these infections are caused by genotype T4 strains.

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