@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{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{seitz_herro_epelbaum_hock_magerl_2006, title={Lattice-plane curvature and small-angle grain boundaries in SiC bulk crystals}, volume={39}, ISSN={["1600-5767"]}, DOI={10.1107/S002188980503298X}, abstractNote={SiC crystals grown by the physical vapour transport process along the [001] direction show a curvature of the crystal growth front in correspondence with the shape of the isotherms. A large radius for the curvature of the isotherms enhances the formation of an extended facet. Under the facet, the lattice planes are flat with a high crystal quality as expressed by rocking-curve half widths of 0.022°. In the non-faceted region, the lattice planes become bent, following the shape of the isotherms with a radius of typically 0.5 to 0.8 m and an increased rocking-curve half width of 0.3°. A reduction of the growth rate from 300 µm h−1to 70 µm h−1does not affect this behaviour significantly. The lattice-plane curvature and the development of the facet are predominantly affected by the shape of the isotherms. For crystals grown in the [015] direction, the lattice planes adjust only in a one-dimensional manner to the isotherms. In all cases, the lattice-plane curvature results from the formation of a high density of small-angle grain boundaries. They are generated by the condensation of dislocations with Burgers vectors in theabplane.}, journal={JOURNAL OF APPLIED CRYSTALLOGRAPHY}, author={Seitz, C and Herro, ZG and Epelbaum, BM and Hock, R and Magerl, A}, year={2006}, month={Feb}, pages={17–23} }
 @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{herro_zhuang_schlesser_collazo_sitar_2006, title={Seeded growth of AlN on N- and Al-polar < 0 0 0 1 > AlN seeds by physical vapor transport}, volume={286}, ISSN={["1873-5002"]}, DOI={10.1016/j.jcrysgro.2005.10.074}, abstractNote={We demonstrated seeded growth of AlN on large-area Al- and N-polar <0 0 0 1>-oriented AlN seeds using the physical vapor transport method (PVT). In both cases, crystals having a diameter of 15 mm were obtained from 5 mm seeds. Based on growth step and terrace width analyses, it was found that the N-polar face was suitable for growth within a large window of growth parameters while the Al-polar seeds yielded high-quality crystals only at low supersaturation.}, number={2}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Herro, ZG and Zhuang, D and Schlesser, R and Collazo, R and Sitar, Z}, year={2006}, month={Jan}, pages={205–208} }
 @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} }