@article{abdelhamid_routh_hagar_bedair_2022, title={Improved LED output power and external quantum efficiency using InGaN templates}, volume={120}, ISSN={["1077-3118"]}, url={https://doi.org/10.1063/5.0084273}, DOI={10.1063/5.0084273}, abstractNote={InGaN templates have recently attracted interest due to their ability to reduce strain in the quantum wells and to induce a red shift in the emission wavelength. For such technology to be competitive, it should outperform the traditional technology for LEDs grown on GaN substrates and offer improved output characteristics. InGaN based LEDs on InyGa1−yN templates with varying In-content of 8% ≤ y ≤ 12% are studied for the same emission wavelength. The electroluminescence, optical output power, and external quantum efficiency of the LEDs are investigated as a function of the In-content in the templates. LEDs on InGaN templates with In-content of 8–10% show better performance than LEDs grown on GaN. This enhancement is attributed to improved radiative recombination as a result of the reduced strain in the quantum wells. However, templates with In-content of ∼10.5% and ∼11% show inferior performance to the LEDs on GaN because the deterioration from the increased defects from the template is stronger than the improvement in the radiative recombination. It can be concluded that the InGaN templates with 8–10% offer a technology for LEDs that is outperforming the traditional GaN technology.}, number={8}, journal={APPLIED PHYSICS LETTERS}, author={Abdelhamid, Mostafa and Routh, Evyn L. and Hagar, Brandon and Bedair, S. M.}, year={2022}, month={Feb} }
 @article{hagar_abdelhamid_routh_colter_bedair_2022, title={Ohmic co-doped GaN/InGaN tunneling diode grown by MOCVD}, volume={121}, ISSN={["1077-3118"]}, url={https://doi.org/10.1063/5.0103152}, DOI={10.1063/5.0103152}, abstractNote={Tunnel junctions (TJs) have recently been proposed as a solution for several III-nitride current problems and to enhance new structures. Reported III-nitride TJs grown by metalorganic chemical vapor deposition (MOCVD) resulted in backward diodes with rectifying behavior in forward bias, even with Mg and Si doping in 1020 cm−3. This behavior limits applications in several device structures. We report a TJ structure based on p+In0.15Ga0.85N/n+In0.05Ga0.95N, where the n-side of the junction is co-doped with Si and Mg and with electron and hole concentrations in the mid-1019 cm−3 for both the n and p dopants. Co-doping creates deep levels within the bandgap that enhances tunneling under forward biased conditions. The TJ structure was investigated on both GaN substrates and InGaN templates to study the impact of strain on the TJ I–V characteristics. The resulting TJ I–V and resistivities reported indicate the potential for this TJ approach in several device structures based on III-nitrides. We are not aware of any previous MOCVD grown TJs that show Ohmic performance in both forward and reverse biases.}, number={5}, journal={APPLIED PHYSICS LETTERS}, author={Hagar, B. G. and Abdelhamid, M. and Routh, E. L. and Colter, P. C. and Bedair, S. M.}, year={2022}, month={Aug} }
 @article{routh_abdelhamid_colter_el-masry_bedair_2021, title={P-type InxGa1-xN semibulk templates (0.02 < x < 0.16) with room temperature hole concentration of mid-10(19) cm(-3) and device quality surface morphology}, volume={119}, ISSN={["1077-3118"]}, url={https://doi.org/10.1063/5.0065194}, DOI={10.1063/5.0065194}, abstractNote={Using the semibulk approach, p-InxGa1−xN semibulk (p-SB) templates were grown with an indium content ranging from 2.4% to 15.2% via metalorganic chemical vapor deposition. When compared to optimized bulk p-GaN, the hole concentration in p-SB with an In content of ∼15.2% increased by two orders of magnitude from 5.22 × 1017 to 5.28 × 1019 cm−3. The resistivity and mobility of the templates decreased gradually from 3.13 Ω · cm and 3.82 cm2/V s for p-GaN to 0.24 Ω · cm and 0.48 cm2/V s for p-SB with an In content of 15.2%. Temperature dependent Hall measurements were conducted to estimate the activation energy of the p-SB template. The p-SB with the In content of ∼15.2% is estimated to have an activation energy of 29 meV. These heavily doped p-SB templates have comparable material qualities to that of GaN. The atomic force microscopy height retraces of p-SB films show device quality surface morphology, with root mean square roughness ranging from 2.53 to 4.84 nm. The current results can impact the performances of several nitride-based devices, such as laser diodes, LEDs, solar cells, and photodetectors.}, number={12}, journal={APPLIED PHYSICS LETTERS}, author={Routh, Evyn L. and Abdelhamid, Mostafa and Colter, Peter and El-Masry, N. A. and Bedair, S. M.}, year={2021}, month={Sep} }
 @article{abdelhamid_routh_shaker_bedair_2021, title={Shifting LED emission from blue to the green gap spectral range using In0.12Ga0.88N relaxed templates}, volume={160}, ISSN={["1096-3677"]}, url={https://doi.org/10.1016/j.spmi.2021.107065}, DOI={10.1016/j.spmi.2021.107065}, abstractNote={InyGa1-yN templates are grown with y ≤ 13.5% and a few nm surface roughness. These templates are used successfully to address two of the main issues facing long wavelength emitting LEDs, mainly the low growth temperature and high values of strain in the quantum wells (QWs). In this work, three LED structures are investigated: the first is a blue LED grown on GaN, the second and third are green LEDs grown on relaxed InyGa1-yN templates with y of about 10% and 12%, respectively. The same multiple quantum wells (MQWs) were used in the three LED structures, with the same well width, barrier width, and growth temperature. The reduced strain in the QWs due to the use of InGaN templates enhances the indium incorporation rate in the QWs. Red shift in emission wavelength of about 100 nm, from 470 nm to 570 nm, was achieved, at low injection current. Optical output power and external quantum efficiency (EQE) measurements showed that at high level of current injection, performance of the blue LED is about twice of the green emitting LEDs on InGaN templates. The current results indicate the potential of the InGaN template approach, with high values of y, in addressing problems facing long wavelength InGaN LEDs.}, journal={SUPERLATTICES AND MICROSTRUCTURES}, author={Abdelhamid, Mostafa and Routh, Evyn L. and Shaker, Ahmed and Bedair, S. M.}, year={2021}, month={Dec} }
 @article{abdelhamid_routh_bedair_2021, title={The dependence of the emission from MQWs on the indium content in the underlying InGaN templates: experimental and modeling results}, volume={36}, ISSN={["1361-6641"]}, DOI={10.1088/1361-6641/abe141}, abstractNote={Abstract}, number={3}, journal={SEMICONDUCTOR SCIENCE AND TECHNOLOGY}, author={Abdelhamid, Mostafa and Routh, Evyn L. and Bedair, S. M.}, year={2021}, month={Mar} }
 @article{routh_abdelhamid_el-masry_bedair_2020, title={Device quality templates of InxGa1-xN (x < 0.1) with defect densities comparable to GaN}, volume={117}, ISSN={["1077-3118"]}, url={https://doi.org/10.1063/5.0015419}, DOI={10.1063/5.0015419}, abstractNote={InGaN/GaN multiple quantum well (MQW) structures currently used in optical devices are based on highly strained InGaN films. The presence of strain reduces quantum efficiency and indium incorporation, two critical parameters in addressing the green gap. We report on the growth of InGaN-relaxed templates on GaN as substrates to reduce the strain in the MQW structures. Relaxation in the InGaN templates, due to the lattice mismatch, is accommodated by the generation of V-pits rather than the formation of misfit dislocations. InxGa1−xN templates (x ∼ 0.1) are grown via a modified semibulk (SB) approach, with a gradually increasing GaN interlayer thickness to provide a mechanism for backfilling of V-pits. We used high-resolution x-ray diffraction rocking curves to quantify the edge-type and screw-type dislocation density present in the SB and compared the results with the etch pit density obtained via atomic force microscopy after treating the SB with a silane etch. Device-quality InGaN templates with defect density in the mid 108 cm−2 were investigated using the above two approaches, with a quality comparable to state-of-the-art GaN.}, number={5}, journal={APPLIED PHYSICS LETTERS}, publisher={AIP Publishing}, author={Routh, Evyn L. and Abdelhamid, Mostafa and El-Masry, N. A. and Bedair, S. M.}, year={2020}, month={Aug} }
 @article{eldred_abdelhamid_reynolds_el-masry_lebeau_bedair_2020, title={Observing relaxation in device quality InGaN templates by TEM techniques}, volume={116}, ISSN={["1077-3118"]}, DOI={10.1063/1.5139269}, abstractNote={Device quality InGaN templates are synthesized using the semibulk (SB) approach. The approach maintains the film's 2D growth and avoids the formation of indium-metal inclusions. The strain relaxation processes of the grown InxGa1−xN templates are accompanied by variations in the indium content (x) and lattice parameters (a and c) across the InGaN template's thickness as the residual strain is continuously decreasing. This strain and lattice parameters' variation creates difficulties in applying standard x-ray Diffraction (XRD) and Reciprocal Space mapping (RSM) techniques to estimate the residual strain and the degree of the elastic strain relaxation. We used high-resolution High-angle annular dark-field scanning transmission electron microscopy and Energy-dispersive x-ray spectroscopy (EDS) to monitor the variations of the indium content, lattice parameters, and strain relaxation across the growing InxGa1−xN templates. We show that strain relaxation takes place by V-pit defect formation. Some of these V-pits are refilled by the GaN interlayers in the InxGa1−xN SB templates, while others propagate to the template surface. We present an alternative approach combining photoluminescence (PL) and EDS for estimating the degree of strain relaxation in these InxGa1−xN templates. The values obtained for the degree of relaxation estimated from TEM studies and PL measurements are within reasonable agreement in this study. Device quality InxGa1−xN templates with x ∼ 0.08, with a degree of relaxation higher than 70%, are achieved.}, number={10}, journal={APPLIED PHYSICS LETTERS}, author={Eldred, Tim B. and Abdelhamid, Mostafa and Reynolds, J. G. and El-Masry, N. A. and LeBeau, James M. and Bedair, S. M.}, year={2020}, month={Mar} }
 @article{abdelhamid_reynolds_el-masry_bedair_2019, title={Growth and characterization of InxGa1-xN (0 < x < 0.16) templates for controlled emissions from MQW}, volume={520}, ISSN={["1873-5002"]}, DOI={10.1016/j.jcrysgro.2019.05.019}, abstractNote={InxGa1−xN (0 < x < 0.16) templates were grown by Metal Organic Chemical Vapor Deposition (MOCVD) using the semibulk (SB) growth approach. We have studied the impact of different SB design parameters such as the number of (InGaN/GaN) periods, InGaN layer thickness (T), and the GaN substrate quality on the SB-template properties, and its degree of relaxation. SIMS characterization measured the variation of indium content (x) in the template, while photoluminescence reflected the indium content at the topmost layers of the SB template. X-ray diffraction techniques measured the average lattice parameters and degree of strain relaxation through the entire InxGa1−xN SB-templates. The SB approach results in superior material quality relative to the bulk grown InGaN, mainly due to its ability to avoid the inclusion of indium-rich clusters and V-pits in the SB templates. The SB approach slows down the relaxation processes and templates as thick as 750 nm are not fully relaxed. We are reporting on methods to enhance the relaxation processes in InxGa1−xN SB-templates. Finally, when InxGa1−xN templates with 0 ≤ x ≤ 0.16 are used as substrates for InGaN/GaN multiple quantum wells, the emission wavelength is shifted from blue to green by changing the indium content in the InxGa1−xN SB-templates. To the best of our knowledge, the current results present the highest indium content reported in InxGa1−xN SB-templates.}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Abdelhamid, Mostafa and Reynolds, J. G. and El-Masry, N. A. and Bedair, S. M.}, year={2019}, month={Aug}, pages={18–26} }