@article{berkman_el-masry_emara_bedair_2008, title={Nearly lattice-matched n, i, and p layers for InGaN p-i-n photodiodes in the 365-500 nm spectral range}, volume={92}, ISSN={["0003-6951"]}, DOI={10.1063/1.2896648}, abstractNote={We report on nearly lattice-matched grown InGaN based p-i-n photodiodes detecting in the 365–500nm range with tunable peak responsivity tailored by the i-layer properties. The growth of lattice matched i- and n-InGaN layer leads to improvement in the device performance. This approach produced photodiodes with zero-bias responsivities up to 0.037A∕W at 426nm, corresponding to 15.5% internal quantum efficiency. The peak responsivity wavelength ranged between 416 and 466nm, the longest reported for III-N photodiodes. The effects of InN content and i-layer thickness on photodiode properties and performance are discussed.}, number={10}, journal={APPLIED PHYSICS LETTERS}, author={Berkman, E. A. and El-Masry, N. A. and Emara, A. and Bedair, S. M.}, year={2008}, month={Mar} }
 @article{jagannadham_berkman_elmasry_2008, title={Thermal conductivity of semi-insulating, p-type, and n-type GaN films on sapphire}, volume={26}, ISSN={["1520-8559"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-42949135532&partnerID=MN8TOARS}, DOI={10.1116/1.2899379}, abstractNote={The thermal conductivity of undoped, n-type, and p-type GaN films deposited on (0001) substrates of sapphire was measured by the 3-ω method in the temperature range between 215 and 300K. The thickness, thermal conductivity, and heat capacity of the individual layers were used to simulate the experimental value of the increment in temperature of the heater using a multilayer model. The thermal conductivity of undoped GaN film was found to be much higher than that of p-type film. Also, the thermal conductivity of n-type GaN film was slightly smaller than that of p-type film. Modeling of the temperature dependence of the thermal conductivity in the films showed that phonon-dopant and three-phonon umklapp scattering are important. Smaller thickness and hence smaller volume fraction of the film with lower dislocation density was also found to be responsible for lower thermal conductivity in n- and p-type GaN films.}, number={3}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A}, author={Jagannadham, K. and Berkman, E. A. and Elmasry, N.}, year={2008}, month={May}, pages={375–379} }
 @article{barletta_berkman_moody_el-masry_emara_reed_bedair_2007, title={Development of green, yellow, and amber light emitting diodes using InGaN multiple quantum well structures}, volume={90}, ISSN={["0003-6951"]}, DOI={10.1063/1.2721133}, abstractNote={The authors present optical and electrical data for long wavelength (573–601nm) InGaN∕GaN multiple quantum well light emitting diodes (LEDs) grown by metal organic chemical vapor deposition. These results are achieved by optimizing the active layer growth temperature and the quantum well width. Also, the p-GaN is grown at low temperature to avoid the disintegration of the InGaN quantum wells with high InN content. A redshift is observed for both the green and yellow LEDs upon decreasing the injection current at low current regime. In the case of the yellow LED, this shift is enough to push emission into the amber (601nm).}, number={15}, journal={APPLIED PHYSICS LETTERS}, author={Barletta, Philip T. and Berkman, E. Acar and Moody, Baxter F. and El-Masry, Nadia A. and Emara, Ahmed M. and Reed, Mason J. and Bedair, S. M.}, year={2007}, month={Apr} }
 @article{mahros_luen_emara_bedair_berkman_el-masry_zavada_2007, title={Magnetic and magnetotransport properties of (AlGaN/GaN): Mg/(GaMnN) heterostructures at room temperature}, volume={90}, ISSN={["0003-6951"]}, DOI={10.1063/1.2749717}, abstractNote={Dilute magnetic semiconductor films (GaMnN) are highly resistive, making transport measurements difficult to achieve. However, when GaMnN films are sandwiched between p-type doped (AlGaN∕GaN) strained-layer superlattices, holes from the superlattice interact with the Mn3+∕2+ ions and transport measurements were realized. The authors have found also that the ferromagnetic properties of GaMnN critically depend on the level of p-type doping in the superlattice. They report anomalous Hall effect measurements in this (AlGaN∕GaN):Mg∕(GaMnN) multilayered structure. The current results also demonstrate the role of carriers, especially holes, in mediating the ferromagnetic properties of GaMnN dilute magnetic semiconductor films.}, number={25}, journal={APPLIED PHYSICS LETTERS}, author={Mahros, Amr M. and Luen, M. O. and Emara, A. and Bedair, S. M. and Berkman, E. A. and El-Masry, N. A. and Zavada, J. M.}, year={2007}, month={Jun} }
 @article{reed_arkun_berkman_elmasry_zavada_luen_reed_bedair_2005, title={Effect of doping on the magnetic properties of GaMnN: Fermi level engineering}, volume={86}, ISSN={["1077-3118"]}, DOI={10.1063/1.1881786}, abstractNote={GaMnN dilute magnetic semiconductor samples, prepared by metalorganic chemical vapor deposition, are shown to exhibit ferromagnetism or even paramagnetism depending upon the type and concentration of extrinsic impurity present in the film. In addition, GaMnN deposited using growth parameters normally yielding a nonferromagnetic film becomes strongly ferromagnetic with the addition of magnesium, an acceptor dopant. Based upon these observations, it seems that ferromagnetism in this material system depends on the relative position of the Mn energy band and the Fermi level within the GaMnN band gap. Only when the Fermi level closely coincides with the Mn-energy level is ferromagnetism achieved. By actively engineering the Fermi energy to be within or near the Mn energy band, room temperature ferromagnetism is realized.}, number={10}, journal={APPLIED PHYSICS LETTERS}, author={Reed, MJ and Arkun, FE and Berkman, EA and Elmasry, NA and Zavada, J and Luen, MO and Reed, ML and Bedair, SM}, year={2005}, month={Mar} }
 @inproceedings{emara_berkman_zavada_el-masry_bedair, title={Strain relaxation in InxGa1-xN/GaN quantum well structures}, volume={8}, number={7-8}, booktitle={Physica status solidi c: current topics in solid state physics, vol 8, no 7-8}, author={Emara, A. M. and Berkman, E. A. and Zavada, J. and El-Masry, N. A. and Bedair, S. M.} }