Publications and Presentations



Research articles published in refereed journals


T. Kinoshita, T. Nagashima, T. Obata, S. Takashima, R. Yamamoto, R. Togashi, Y. Kumagai, R. Schlesser, R. Collazo, A. Koukitu, Z. Sitar, "Fabrication of vertical Schottky barrier diodes on n-type freestanding AlN substrates grown by hydride vapor phase epitaxy," Appl. Phys. Express. 8 (6), 061003 (2015).

G. Callsen, M.R. Wagner, J.S. Reparaz, F. Nippert, T. Kure, S. Kalinowski, A. Hoffmann, M.J. Ford, M.R. Phillips, R.F. Dalmau, R. Schlesser, R. Collazo, Z. Sitar, "Phonon pressure coefficients and deformation potentials of wurtzite AlN determined by uniaxial pressure-dependent Raman measurements," Phys. Rev. B 90 (20), 205206 (2014).

B. E. Gaddy, Z. Bryan, I. Bryan, J. Xie, R. Dalmau, B. Moody, Y. Kumagai, T. Nagashima, Y. Kubota, T. Kinoshita, A. Koukitu, R. Kirste, Z. Sitar, R. Collazo, D. L. Irving, "The role of the carbon-silicon complex in eliminating deep ultraviolet absorption in AlN," Appl. Phys. Lett. 104, 202106 (2014).

T. Zhou, B. Raghothamachar, F. Wu, R. Dalmau, B. Moody, S. Craft, R. Schlesser, M. Dudley, Z. Sitar, "Characterization of Threading Dislocations in PVT-Grown AlN Substrates via x-Ray Topography and Ray Tracing Simulation," J. Electron. Materials 43 (4), 838 (2014).

T. Kinoshita, T. Obata, T. Nagashima, H. Yanagi, B. Moody, S. Mita, S. Inoue, Y. Kumagai, A. Koukitu, Z. Sitar, "Performance and reliability of deep-ultraviolet light-emitting diodes fabricated on AlN substrates prepared by hydride vapor phase epitaxy," Appl. Phys. Express 6, 092103 (2013).

B. Neuschl, K. Thonke, M. Feneberg, R. Goldhahn, T. Wunderer, Z. Yang, N. M. Johnson, J. Xie, S. Mita, A. Rice, R. Collazo, Z. Sitar, "Direct determination of the silicon donor ionization energy in homoepitaxial AlN from photoluminescence two-electron transitions," Appl. Phys. Lett. 103, 122105 (2013).

M. Bobea, J. Tweedie, I. Bryan, Z. Bryan, A. Rice, R. Dalmau, J. Xie, R. Collazo, Z. Sitar, "X-ray characterization techniques for the assessment of surface damage in crystalline wafers: A model study in AlN," J. Appl. Phys. 113, 123508 (2013).

B. Raghothamachar, Y. Yang, R. Dalmau, B. Moody, S. Craft, R. Schlesser, M. Dudley, Z. Sitar, "Defect generation mechanisms in PVT-grown AlN single crystal boules," Mat. Sci. Forum 740, 91 (2013).

B. E. Gaddy, Z. Bryan, I. Bryan, R Kirste, J. Xie, R. Dalmau, B. Moody, Y. Kumagai, T. Nagashima, Y. Kubota, T. Kinoshita, A. Koukitu, Z. Sitar, R. Collazo, D. L. Irving, "Vacancy compensation and related donor-acceptor pair recombination in bulk AlN," Appl. Phys. Lett. 103 (16), 161901 (2013).

J. Xie, S. Mita, Z. Bryan, W. Guo, L. Hussey, B. Moody, R. Schlesser, R. Kirste, M. Gerhold, R. Collazo, and Z. Sitar, "Lasing and longitudinal cavity modes in photo-pumped deep ultraviolet AlGaN heterostructures," Appl. Phys. Lett. 102, 171102 (2013).

T. Kinoshita, K. Hironaka, T. Obata, T. Nagashima, R. Dalmau, R. Schlesser, B. Moody, J. Xie, S. Inoue, Y. Kumagai, A. Koukitu, Z. Sitar, "Deep-ultraviolet light-emitting diodes fabricated on AlN substrates prepared by hydride vapor phase epitaxy," Appl. Phys. Express 5 (12) 122101 (2012).

T. Nagashima, Y. Kubota, T. Kinoshita, Y. Kumagai, J. Xie, R. Collazo, H. Murakami, H. Okamoto, A. Koukitu, Z. Sitar, "Structural and optical properties of carbon-doped AlN substrates grown by hydride vapor phase epitaxy using AlN substrates prepared by physical vapor transport," Appl. Phys. Express 5, 125501 (2012).

Y. Kumagai, Y. Kubota, T. Nagashima, T. Kinoshita, R. Dalmau, R. Schlesser, B. Moody, J. Xie, H. Murakami, A. Koukitu, and Z. Sitar, "Preparation of a freestanding AlN substrate from a thick AlN layer grown by hydride vapor phase epitaxy on a bulk AlN substrate prepared by physical vapor transport," Applied Physics Express 5, 055504 (2012).

R. Collazo, J. Xie, B.E. Gaddy, Z. Bryan, R. Kirste, M. Hoffmann, R. Dalmau, B. Moody, Y. Kumagai, T. Nagashima, Y. Kubota, T. Kinoshita, A. Koukitu, D.L. Irvine, and Z. Sitar, "On the origin of the 265 nm absorption band in AlN bulk crystals," Appl. Phys. Lett. 100, 191914 (2012).

B. Raghothamachar, R. Dalmau, B. Moody, S. Craft, R. Schlesser, J. Xie, R. Collazo, M. Dudley, and Z. Sitar, "Low defect density bulk AlN substrates for high performance electronics and optoelectronics," Materials Science Forum 717-720, 1287-90 (2012).

M. Feneberg, B. Neuschl, K. Thonke, R. Collazo, A. Rice, Z. Sitar, R. Dalmau, J. Xie, S. Mita, R. Goldhahn, "Sharp bound and free exciton lines from homoepitaxial AlN," Physica Status Solidi a 208 (7), 1520 (2011).

B. Neuschl, K. Thonke, M. Feneberg, S. Mita, J. Xie, R. Dalmau, R. Collazo, Z. Sitar, "Optical identification of silicon as a shallow donor in MOVPE grown homoepitaxial AlN," Physica Status Solidi b 249 (3), 511 (2011).

T. Wunderer, C. L. Chua, Z. Yang, J. E. Northrup, M. Kneissl, G. A. Garrett, H. Shen, M. Wraback, B. Moody, H. S. Craft, R. Schlesser, R. F. Dalmau, Z. Sitar, N. M. Johnson, "Optically pumped UV lasers grown on bulk AlN substrates," Physica Status Solidi c 9 (3-4), 822 (2011).

R. Dalmau, B. Moody, J. Xie, R. Collazo, and Z. Sitar, "Characterization of dislocation arrays in AlN single crystals grown by PVT," Phys. status solidi A 208 (7), 1545-7 (2011).

S. Mita, R. Collazo, A. Rice, J. Tweedie, J. Xie, R. Dalmau and Z. Sitar, "Impact of Gallium Supersaturation on the Growth of N-polar GaN," Physica Status Solidi c 8 (7-8), 2078-80 (2011).

H. S. Craft, A. L. Rice, R. Collazo, Z. Sitar, and J. P. Maria, "Spectroscopic measurements of the surface stoichiometry of chemical vapor deposited GaN," Appl. Phys. Lett. 98, 082110 (2011).

J. Xie, S. Mita, A. Rice, J. Tweedie, L. Hussey, R. Collazo, and Z. Sitar, "Strain in Si doped GaN and the Fermi level effect," Appl. Phys. Lett. 98, 202101 (2011).

R. Dalmau, B. Moody, R. Schlesser, S. Mita, J. Xie, M. Feneberg, B. Neuschl, K. Thonke, R. Collazo, A. Rice, J. Tweedie, and Z. Sitar, "Growth and characterization of AlN and AlGaN epitaxial films on AlN single crystal substrates," J. Electrochem. Soc., 158(5) (2011) H530-H535.

R. Collazo, S. Mita, J. Xie, A. Rice, J. Tweedie, R. Dalmau, and Z. Sitar, "Progress on n-type doping of AlGaN alloys on AlN single crystal substrates for UV optoelectronic applications," Physica Status Solidi (C), DOI 10.1002/pssc.201000964 (2011).

R. Dalmau, B. Moody, R. Schlesser, S. Mita, J. Xie, M. Feneberg, B. Neuschl, K. Thonke, R. Collazo, A. Rice, J. Tweedie, and Z. Sitar, "Growth and characterization of AlN and AlGaN epitaxial films on AlN single crystal substrates," ECS Transactions, SOTAPOCS 52, 33(13) (2010) 43-54.

A. L. Rice, R. Collazo, J. Tweedie, R. Dalmau, S. Mita, J. Xie, and Z. Sitar, "Surface preparation and homoepitaxial deposition of AlN on (0001)-oriented AlN substrates by metalorganic chemical vapor deposition," J. Appl. Phys. 108, 043510 (2010).

Z.G. Herro, D. Zhuang, R. Schlesser, Z. Sitar, “Growth of AlN single crystalline boules,” J. Crystal Growth, 312, 2519-2521 (2010).

Lu P, Collazo R, Dalmau R, Durkaya G, Dietz N, Raghothamachar B, Dudley M, Sitar Z, “Seeded growth of AlN bulk crystals in m- and c-orientation,” J. Cryst. Growth, 312 (1), 58-63 (2009).

P. Lu, J. H. Edgar, C. Cao, K. Hohn, R. Dalmau, R. Schlesser and Z. Sitar, "Seeded growth of AlN on SiC substrates and defect characterization", J. Cryst. Growth 310, 2464-2470 (2008).


Research articles published in refereed proceedings


M. Buegler, S. Gamage, R. Atalay, J. Wang, I. Senevirathna, R. Kirste, T. Xu, M. Jamil, I. Ferguson, J. Tweedie, R. Collazo, A. Hoffmann, Z. Sitar, and N. Dietz, "Reactor pressure - growth temperature relation for InN epilayers grown by high-pressure CVD," SPIE 7784, doi: 10.1117/12.860952 , paper# 77840F-1-7 (2010).

R. F. Davis, S. M. Bishop, S. Mita, R. Collazo, Z. J. Reitmeier and Z. Sitar," Epitaxial Growth Of Gallium Nitride, AIP Conf. Proc. 916, 520 (2007).

D. Zhuang, Z. G. Herro, X. Li, R. Schlesser and Z. Sitar, "Wet Etching of Bulk AlN Crystals," Mater. Res. Soc. Symp. Proc. 955, 0955-I07-10 (2007).


Invited book chapters


R. Dalmau and Z. Sitar, "AlN bulk crystal growth by physical vapor transport," in Springer Handbook of Crystal Growth, edited by G. Dhanaraj, K. Byrappa, V. Prasad, M. Dudley, p. 821 (Springer Verlag, Berlin, 2010).

D. Ehrentraut, Z. Sitar, "Advances in Bulk Crystal Growth of AlN and GaN," MRS Bull. 34, 259-265 (2009).

R. Dalmau, Z. Sitar, "Sublimation growth of AlN crystals," in Encyclopedia of Materials: Science and Technology Updates, edited by K. H. J. Buschow, R. W. Cahn, M. C. Flemings, B. Ilschner, E. J. Kramer, S. Mahajan, and P. Veyssière (Elsevier, Oxford, 2005).

R. Collazo, R. Schlesser, Z. Sitar, “High field transport in AlN,” GaN-based materials and devices, M.S. Shur, R.F. Davis eds, Special topics in electronics and systems, vol 33, p.p. 155-174, World scientific publishing 2004.