Publications and Presentations

Research articles published in refereed journals

S. Rathkanthiwar, P. Reddy, B. Moody, C. Quiñones-García, P. Bagheri, D. Khachariya, R. Dalmau, S. Mita, R. Kirste, R. Collazo, Z. Sitar, "High p-conductivity in AlGaN enabled by polarization field engineering," Appl. Phys. Lett. 122, 152105 (2023).

S. Hu, H. Fan, Y. Liu, H. Peng, Q. Cheng, Z. Chen, R. Dalmau, J. Britt, R. Schlesser, B. Raghothamachar, M. Dudley, "Characterization of prismatic slip in PVT-Grown AlN crystals, J. Cryst. Growth 584, 126548 (2022).

K. Goto, N. Takekawa, T. Nagashima, R. Yamamoto, G. Pozina, R. Dalmau, R. Schlesser, R. Collazo, B. Monemar, Z. Sitar, M. Bockowski, Y. Kumagai, "Study of dislocations in homo- and hetero-epitaxially grown AlN layers," Physica Status Solidi a 2020, 2000465 (2020).

R. Yamamoto, N. Takekawa, K. Goto, T. Nagashima, R. Dalmau, R. Schlesser, H. Murakami, R. Collazo, B. Monemar, Z. Sitar, Y. Kumagai, "Hydride vapor phase epitaxy of Si-doped AlN layers using SiCl4 as a doping gas," J. Cryst. Growth 545, 125730 (2020).

R. Dalmau, J. Britt, H. Fang, B. Raghothamachar, M. Dudley, R. Schlesser, "X-ray topography characterization of large diameter AlN single crystal substrates," Mater. Sci. Forum 1004, 63 (2020).

D. Liu, S. J. Cho, H. Zhang, C. R. Carlos, A.l R. K. Kalapala, J. Park, J. Kim, R. Dalmau, J. Gong, B. Moody, X. Wang, J. D. Albrecht, W. Zhou, Z. Ma, "Influences of screw dislocations on electroluminescence of AlGaN/AlN-based UVC LEDs," AIP Adv. 9, 085128 (2019).

S. J. Cho, D. Liu, J. Seo, R. Dalmau, K. Kim, J. Park, J. Gong, D. Zhao, F. Wang, X. Yin, Y. H. Jung, I. Lee, M. Kim, X. Wang, J. D. Albrecht, W. Zhou, B. Moody, Z. Ma, “P-type silicon as hole supplier for nitride-based UVC LEDs,” New J. Phys. 21, 23011 (2019).

D. Liu, S. J. Cho, J. Park, J. Gong, J. Seo, R. Dalmau, D. Zhao, K. Kim, M. Kim, A. R. Kalapala, J. D. Albrecht, W. Zhou, B. Moody, Z. Ma, "226 nm AlGaN/AlN UV LEDs using p-type Si for hole injection and UV reflection," Appl. Phys. Lett. 113, 11111 (2018).

D. Liu, S. J. Cho, J. Park, J. Seo, R. Dalmau, D. Zhao, K. Kim, J. Gong, M. Kim, I. Lee, J. D. Albrecht, W. Zhou, B. Moody, Z. Ma, "229 nm UV LEDs on aluminum nitride single crystal substrates using p-type silicon for increased hole injection," Appl. Phys. Lett. 112, 81101 (2018).

R. Dalmau, H. S. Craft, J. Britt, E. Paisley, B. Moody, J. Guo, Y. Ji, B. Raghothamachar, M. Dudley, R. Schlesser, "High quality AlN single crystal substrates for AlGaN-based devices," Mater. Sci. Forum 924, 923 (2018).

S. Tojo, R. Yamamoto, R. Tanaka, Q. T. Thieu, R. Togashi, T. Nagashima, T. Kinoshita, R. Dalmau, R. Schlesser, H. Murakami, R. Collazo, A. Koukitu, B. Monemar, Z. Sitar, Y. Kumagai, "Influence of high-temperature processing on the surface properties of bulk AlN substrates," J. Cryst. Growth 446, 33 (2016).

T. Kim, J. Kim, R. Dalmau, R. Schlesser, E. Preble, X. Jiang, "High-temperature electromechanical characterization of AlN single crystals," IEEE Trans. On Ultrasonics, Ferroelectrics, and Frequency Control, 62(10), 1880 (2015).

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) H530-H535 (2011).

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).

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).

H. J. Kim, S. Choi, D. Yoo, J. H. Ryou, R. D. Dupuis, R. F. Dalmau, P. Lu, Z. Sitar, "Modulated precursor flow epitaxial growth of AlN layers on native AlN substrates by metal-organic chemical vapor deposition," Appl. Phys. Lett. 93(2), 22103 (2008).

R. Dalmau, R. Collazo, S. Mita, Z. Sitar, "X-ray photoelectron spectroscopy characterization of aluminum nitride surface oxides: thermal and hydrothermal evolution," J. Electron. Mater. 36(4), 414-419 (2007).

Research articles published in refereed proceedings

R. Dalmau, S. Kirby, J. Britt, R. Schlesser, "Deep level defects in AlN studied by UV-Visible spectroscopy," ECS Transactions 104(7), 49 (2022).

S. Hu, H. Fan, Y. Liu, H. Peng, T. Ailihuamaer, Q. Cheng, Z. Chen, R. Dalmau, J. Britt, R. Schlesser, B. Raghothamachar, M. Dudley, "Prismatic slip in AlN crystals grown by PVT," ECS Transactions 104(7), 57 (2021).

R. Dalmau, S. Kirby, J. Britt, R. Schlesser, "Complex relative permittivity of UV-C transparent AlN," ECS Transactions 104(7), 49 (2021).

R. Dalmau, J. Britt, R. Schlesser, "Insights into the UV-C optical absorption of AlN substrates grown by PVT," ECS Transactions 98(6), 3 (2020).

R. Dalmau, J. Britt, B. Moody, R. Schlesser, "X-ray metrology of AlN single crystal substrates," ECS Transactions 92(7), 113-121 (2019).

A. R. K. Kalapala, D. Liu, S. J. Cho, J. Park, D. Zhao, R. Dalmau, J. D. Albrecht, B. Moody, Z. Ma, W. Zhou, "Optically pumped room temperature low threshold deep UV lasers grown on native AlN substrates," Proc. SPIE 10918, Gallium Nitride Materials and Devices XIV, 109180I (2019).

R. Dalmau, B. Moody, “Polarization-induced doping in AlGaN epilayers grown on AlN single crystal substrates,” ECS Transactions 86(12), 31 (2018).

R. Dalmau, H. S. Craft, R. Schlesser, S. Mita, J. Smart, C. Hitchcock, G. Pandey, T. P. Chow, B. Moody, "Progress and challenges of AlGaN Schottky diodes grown on AlN substrates," ECS Transactions 80(7), 217 (2017).

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) 43-54 (2010).

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.