@article{herro_zhuang_schlesser_sitar_2010, title={Growth of AlN single crystalline boules}, volume={312}, ISSN={["1873-5002"]}, DOI={10.1016/j.jcrysgro.2010.04.005}, abstractNote={We have obtained high-quality, crack-free AlN wafers using a convex thermal field inside the growth chamber. Free-standing AlN boules of 15 mm in height and 15 mm in diameter were grown. The carbon concentration was found to be similar in all parts of the boule (∼8×1018 cm−3) while the initial O concentration was higher (∼1×1019 cm−3) and slightly decreased during growth. It was found that O incorporated differently on different crystallographic faces. High resolution XRD showed a continuous improvement in crystal quality as a function of boule length. The full width at half maximum (FWHM) of the double crystal rocking curves decreased from 78 in at the beginning of growth to 13 in at the growth end. To the best of our knowledge, this is the first report on impurity incorporation on different crystallographic facets obtained from the same boule.}, number={18}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Herro, Z. G. and Zhuang, D. and Schlesser, R. and Sitar, Z.}, year={2010}, month={Sep}, pages={2519–2521} }
 @article{cai_zheng_zhang_zhuang_herro_schlesser_sitar_2007, title={Effect of thermal environment evolution on A1N bulk sublimation crystal growth}, volume={306}, ISSN={["0022-0248"]}, DOI={10.1016/j.jcrysgro.2007.04.037}, abstractNote={To obtain a large and thick AlN single crystal during sublimation growth, it is very important to maintain the thermal environment suitable for growth inside the crucible during a long period of time (>50 h). In this paper, an in-house developed integrated model capable of describing inductive, radiative and conductive heat transfer will be used to simulate the transient behavior of thermal environment inside the crucible during a 40-h experiment growth. Effects of graphite insulation degradation on temperature distribution inside the crucible will be investigated. Simulation results will be compared with the experimental data to study the effects of the insulation degradation-induced particle deposition, geometric variation of source material and crystal size enlargement on the temperature distribution in the crucible and the growth rate. The relationship between graphite insulation degradation and power input change of the induction-heated system will be established. The evolution of temperature difference between the source material and crystal, which is the driving force for growth, will be presented. This study will also provide the explanation of mechanism underling substantial reduction of growth rate after a long experiment run.}, number={1}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Cai, D. and Zheng, L. L. and Zhang, H. and Zhuang, D. and Herro, Z. G. and Schlesser, R. and Sitar, Z.}, year={2007}, month={Aug}, pages={39–46} }
 @article{gu_edgar_raghothamachar_dudley_zhuang_sitar_coffey_2007, title={Sublimation growth of aluminum nitride on silicon carbide substrate with aluminum nitride-silicon carbide alloy transition layer}, volume={22}, ISSN={["2044-5326"]}, DOI={10.1557/JMR.2007.0077}, abstractNote={The advantages of depositing AlN–SiC alloy transition layers on SiC substrates before the seeded growth of bulk AlN crystals were examined. The presence of AlN–SiC alloy layers helped to suppress the SiC decomposition by providing vapor sources of silicon and carbon. In addition, cracks in the final AlN crystals decreased from ∼5 × 106/mm2 for those grown directly on SiC substrates to less than 1 × 106/mm2 for those grown on AlN–SiC alloy layers because of the intermediate lattice constants and thermal expansion coefficient of AlN–SiC. X-ray diffraction confirmed the formation of pure single-crystalline AlN upon both AlN–SiC alloys and SiC substrates. X-ray topography (XRT) demonstrated that strains present in the AlN crystals decreased as the AlN grew thicker. However, the XRT for AlN crystals grown directly on SiC substrates was significantly distorted with a high overall defect density compared to those grown on AlN–SiC alloys.}, number={3}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Gu, Z. and Edgar, J. H. and Raghothamachar, B. and Dudley, M. and Zhuang, D. and Sitar, Z. and Coffey, D. W.}, year={2007}, month={Mar}, pages={675–680} }
 @article{raghothamachar_bai_dudley_dalmau_zhuang_herro_schlesser_sitar_wang_callahan_et al._2006, title={Characterization of bulk grown GaN and AlN single crystal materials}, volume={287}, ISSN={["1873-5002"]}, DOI={10.1016/j.jcrysgro.2005.11.042}, abstractNote={Sublimation method, spontaneously nucleated as well as seeded on SiC substrates, has been employed for growing AlN bulk crystals. For GaN growth, in addition to the sublimation method using sapphire substrates, ammonothermal growth (analogous to the hydrothermal method) on HVPE GaN seeds is also being used. Thick plates/films of AlN and GaN grown by these methods have been characterized by synchrotron white beam X-ray topography (SWBXT) and high resolution X-ray diffraction (HRXRD). Results from a recent set of growth experiments are discussed.}, number={2}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Raghothamachar, B and Bai, J and Dudley, M and Dalmau, R and Zhuang, DJ and Herro, Z and Schlesser, R and Sitar, Z and Wang, BG and Callahan, M and et al.}, year={2006}, month={Jan}, pages={349–353} }
 @article{zhuang_herro_schlesser_raghothamachar_dudley_sitar_2006, title={Seeded growth of AlN crystals on nonpolar seeds via physical vapor transport}, volume={35}, ISSN={["0361-5235"]}, DOI={10.1007/s11664-006-0141-x}, number={7}, journal={JOURNAL OF ELECTRONIC MATERIALS}, author={Zhuang, D. and Herro, Z. G. and Schlesser, R. and Raghothamachar, B. and Dudley, M. and Sitar, Z.}, year={2006}, month={Jul}, pages={1513–1517} }
 @article{zhuang_herro_schlesser_sitar_2006, title={Seeded growth of AlN single crystals by physical vapor transport}, volume={287}, ISSN={["0022-0248"]}, DOI={10.1016/j.jcrysgro.2005.11.047}, abstractNote={Seeded growth of AlN single crystals was achieved in an induction-heated, high-temperature reactor. The growth process was based on physical vapor transport (PVT), where presintered AlN powder was used as source material. AlN seeds were cut from a boule containing large single crystalline grains, which were grown by natural grain expansion of an initially polycrystalline, self-seeded deposit. Seeded growth was interrupted several times in order to refill the AlN powder source and a dedicated process scheme was used to ensure epitaxial re-growth on the seed surface after each exposure to air. The single crystalline seed expanded laterally at an angle of 45° resulting in an 18 mm large AlN single crystal. The crystal expansion rate, crystalline orientation, as well as growth morphology were characterized by optical microscopy and X-ray diffraction, respectively.}, number={2}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Zhuang, D and Herro, ZG and Schlesser, R and Sitar, Z}, year={2006}, month={Jan}, pages={372–375} }