@article{davis_gehrke_linthicum_preble_rajagopal_ronning_zorman_mehregany_2001, title={Conventional and pendeo-epitaxial growth of GaN(0001) thin films on Si(111) substrates}, volume={231}, ISSN={["1873-5002"]}, DOI={10.1016/S0022-0248(01)01462-2}, abstractNote={Single-crystal wurtzitic GaN(0 0 0 1) films have been grown via conventional methods on high-temperature AlN(0 0 0 1) buffer layers previously deposited on 3C-SiC(1 1 1)/Si(1 1 1) substrates using metal organic vapor phase epitaxy (MOVPE). Formation of the 3C-SiC transition layer employed a carburization step and the subsequent deposition of epitaxial 3C-SiC(1 1 1) on the Si(1 1 1) surface using atmospheric pressure chemical vapor deposition (APCVD) for both processes. Similar films, except with significantly reduced dislocation densities, have been grown via pendeo-epitaxy (PE) from the (112̄0) sidewalls of silicon nitride masked, raised, rectangular, and [11̄00] oriented GaN stripes etched from films conventionally grown on similarly prepared, Si-based, multilayer substrates. The FWHM of the (0 0 0 2) X-ray diffraction peak of the conventionally grown GaN was 1443 arcsec. The FWHM of the photoluminescence (PL) spectra for the near band-edge emission on these films was 19 meV. Tilting in the coalesced PE-grown GaN epilayers of 0.2° was confined to the areas of lateral overgrowth over the masks; no tilting was observed in the material suspended above the trenches. The strong, low-temperature PL band-edge peak at 3.456 eV with an FWHM of 17 meV in the PE films was comparable to that observed in PE GaN films grown on AlN/6H-SiC(0 0 0 1) substrates.}, number={3}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Davis, RF and Gehrke, T and Linthicum, KJ and Preble, E and Rajagopal, P and Ronning, C and Zorman, C and Mehregany, M}, year={2001}, month={Oct}, pages={335–341} }
 @misc{ronning_carlson_davis_2001, title={Ion implantation into gallium nitride}, volume={351}, ISSN={["1873-6270"]}, DOI={10.1016/S0370-1573(00)00142-3}, abstractNote={This comprehensive review is concerned with studies regarding ion implanted gallium nitride (GaN) and focuses on the improvements made in recent years. It is divided into three sections: (i) structural properties, (ii) optical properties and (iii) electrical properties. The first section includes X-ray diffraction (XRD), transmission electron microscopy (TEM), secondary ion mass spectroscopy (SIMS), Rutherford Backscattering (RBS), emission channeling (EC) and perturbed γγ-angular correlation (PAC) measurements on GaN implanted with different ions and doses at different temperatures as a function of annealing temperature. The structural changes upon implantation and the respective recovery upon annealing will be discussed. Several standard and new annealing procedures will be presented and discussed. The second section describes mainly photoluminescence (PL) studies, however, the results will be discussed with respect to Raman and ellipsometry studies performed by other groups. We will show that the PL-signal is very sensitive to the processes occurring during implantation and annealing. The results of Hall and C–V measurements on implanted GaN are presented in Section 3. We show and discuss the difficulties in achieving electrical activation. However, optical and electrical properties are both a result of the structural changes upon implantation and annealing. Each section will be critically discussed with respect to the existing literature, and the main conclusions are drawn from the interplay of the results obtained from the different techniques used/reviewed.}, number={5}, journal={PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS}, author={Ronning, C and Carlson, EP and Davis, RF}, year={2001}, month={Sep}, pages={349–385} }
 @article{ronning_dalmer_uhrmacher_restle_vetter_ziegeler_hofsass_gehrke_jarrendahl_davis_2000, title={Ion implanted dopants in GaN and AlN: Lattice sites, annealing behavior, and defect recovery}, volume={87}, ISSN={["1089-7550"]}, DOI={10.1063/1.372154}, abstractNote={The recovery of structural defects in gallium nitride (GaN) and aluminum nitride (AlN) after implantation of In+111 and Sr+89 in the dose range (0.1–3) 1013 cm−2 and ion energies of 60–400 keV has been investigated as a function of annealing temperature with emission channeling (EC) and perturbed γγ angular correlation spectroscopy. The implanted In and Sr atoms occupied substitutional sites in heavily perturbed surroundings of point defects after room temperature implantation. No amorphization of the lattice structure was observed. The point defects could be partly removed after annealing to 1473 K for 10–30 min. Lattice site occupation of implanted light alkalis, Na+24 in GaN and AlN as well as Li+8 in AlN, were also determined by EC as a function of implantation and annealing temperature. These atoms occupied mainly interstitial sites at room temperature. Lithium diffusion and the occupation of substitutional sites was observed in GaN and AlN at implantation temperatures above 700 K. A lattice site change was also observed for sodium in AlN, but not in GaN after annealing to 1073 K for 10 min.}, number={5}, journal={JOURNAL OF APPLIED PHYSICS}, author={Ronning, C and Dalmer, M and Uhrmacher, M and Restle, M and Vetter, U and Ziegeler, L and Hofsass, H and Gehrke, T and Jarrendahl, K and Davis, RF}, year={2000}, month={Mar}, pages={2149–2157} }
 @article{gehrke_linthicum_preble_rajagopal_ronning_zorman_mehregany_davis_2000, title={Pendeo-epitaxial growth of gallium nitride on silicon substrates}, volume={29}, ISSN={["0361-5235"]}, DOI={10.1007/s11664-000-0068-6}, number={3}, journal={JOURNAL OF ELECTRONIC MATERIALS}, author={Gehrke, T and Linthicum, KJ and Preble, E and Rajagopal, P and Ronning, C and Zorman, C and Mehregany, M and Davis, RF}, year={2000}, month={Mar}, pages={306–310} }
 @article{ronning_hofsass_stotzler_deicher_carlson_hartlieb_gehrke_rajagopal_davis_2000, title={Photoluminescence characterization of Mg implanted GaN}, volume={5}, number={2000}, journal={MRS Internet Journal of Nitride Semiconductor Research}, author={Ronning, C. and Hofsass, H. and Stotzler, A. and Deicher, M. and Carlson, E. P. and Hartlieb, P. J. and Gehrke, T. and Rajagopal, P. and Davis, R. F.}, year={2000}, pages={U622–628} }
 @article{ronning_linthicum_carlson_hartlieb_thomson_gehrke_davis_1999, title={Characterization of Be-implanted GaN annealed at high temperatures}, volume={4S1}, number={G3.17}, journal={MRS Internet Journal of Nitride Semiconductor Research}, author={Ronning, C. and Linthicum, K. J. and Carlson, E. P. and Hartlieb, P. J. and Thomson, D. B. and Gehrke, T. and Davis, R. F.}, year={1999} }
 @article{feldermann_merk_hofsass_ronning_zheleva_1999, title={Room temperature growth of cubic boron nitride}, volume={74}, ISSN={["1077-3118"]}, DOI={10.1063/1.123613}, abstractNote={Boron nitride thin films were deposited at room temperature with various ion energies by mass selected ion beam deposition on cubic boron nitride (c-BN) previously nucleated on Si (100) substrates at a higher temperature. Selective area diffraction, electron energy loss, and infrared spectroscopy results reveal continued growth of the cubic phase. The reported temperature threshold of about 150 °C for c-BN film formation is therefore unmistakably related to the initial nucleation of c-BN, whereas the growth of c-BN appears to be temperature independent. The latter is in accordance with predictions of the cylindrical thermal spike growth model recently proposed by our group.}, number={11}, journal={APPLIED PHYSICS LETTERS}, author={Feldermann, H and Merk, R and Hofsass, H and Ronning, C and Zheleva, T}, year={1999}, month={Mar}, pages={1552–1554} }
 @article{king_davis_ronning_nemanich_1999, title={Valence band discontinuity of the (0001) 2H-GaN/(111) 3C-SiC interface}, volume={28}, ISSN={["0361-5235"]}, DOI={10.1007/s11664-999-0145-4}, number={12}, journal={JOURNAL OF ELECTRONIC MATERIALS}, author={King, SW and Davis, RF and Ronning, C and Nemanich, RJ}, year={1999}, month={Dec}, pages={L34–L37} }
 @article{king_davis_ronning_benjamin_nemanich_1999, title={Valence band discontinuity, surface reconstruction, and chemistry of (0001), (000(1)over-bar), and (1(1)over-bar-00) 2H-AlN/6H-SiC interfaces}, volume={86}, ISSN={["0021-8979"]}, DOI={10.1063/1.371391}, abstractNote={A detailed examination of the valence band discontinuity (ΔEv) formed at the (0001), (0001̄), and (11̄00) interfaces between 2H–AlN and 6H–SiC has been conducted using x-ray and UV photoelectron spectroscopies. The ΔEv was observed to range from 0.6–2.0 eV depending on the growth direction (i.e., AlN on SiC vs SiC on AlN), as well as the crystallographic orientation, cut of the SiC substrate (i.e., on versus off axis), and SiC surface reconstruction and stoichiometry. A ΔEv of 1.4–1.5 eV was observed for AlN grown on (3×3) (0001)Si6H–SiC on-axis substrates; a ΔEv of 0.9–1.0 eV was observed for off-axis substrates with the same surface reconstruction. The values of ΔEv for AlN grown on (√3×√3)R30°(0001) 6H–SiC on-and-off-axis substrates were 1.1–1.2 eV. A larger valence band discontinuity of 1.9–2.0 eV was determined for 3C–SiC grown on (0001) 2H–AlN. Smaller values of ΔEv of 0.6–0.7 and 0.8–0.9 eV were observed for AlN grown on on-axis (0001̄)C and (11̄00)6H–SiC substrates, respectively.}, number={8}, journal={JOURNAL OF APPLIED PHYSICS}, author={King, SW and Davis, RF and Ronning, C and Benjamin, MC and Nemanich, RJ}, year={1999}, month={Oct}, pages={4483–4490} }
 @article{ronning_feldermann_merk_hofsass_reinke_thiele_1998, title={Carbon nitride deposited using energetic species: A review on XPS studies}, volume={58}, number={4}, journal={Physical Review. B, Condensed Matter and Materials Physics}, author={Ronning, C. and Feldermann, H. and Merk, R. and Hofsass, H. and Reinke, P. and Thiele, J. U.}, year={1998}, pages={2207–2215} }
 @article{king_barnak_bremser_tracy_ronning_davis_nemanich_1998, title={Cleaning of AlN and GaN surfaces}, volume={84}, ISSN={["0021-8979"]}, DOI={10.1063/1.368814}, abstractNote={Successful ex situ and in situ cleaning procedures for AlN and GaN surfaces have been investigated and achieved. Exposure to HF and HCl solutions produced the lowest coverages of oxygen on AlN and GaN surfaces, respectively. However, significant amounts of residual F and Cl were detected. These halogens tie up dangling bonds at the nitride surfaces hindering reoxidation. The desorption of F required temperatures >850 °C. Remote H plasma exposure was effective for removing halogens and hydrocarbons from the surfaces of both nitrides at 450 °C, but was not efficient for oxide removal. Annealing GaN in NH3 at 700–800 °C produced atomically clean as well as stoichiometric GaN surfaces.}, number={9}, journal={JOURNAL OF APPLIED PHYSICS}, author={King, SW and Barnak, JP and Bremser, MD and Tracy, KM and Ronning, C and Davis, RF and Nemanich, RJ}, year={1998}, month={Nov}, pages={5248–5260} }
 @article{king_ronning_davis_benjamin_nemanich_1998, title={Dependence of (0001) GaN/AlN valence band discontinuity on growth temperature and surface reconstruction}, volume={84}, ISSN={["0021-8979"]}, DOI={10.1063/1.368355}, abstractNote={X ray and ultraviolet photoelectron spectroscopies have been used to determine the heterojunction valence band discontinuity at the (0001) GaN/AlN interface. Type I discontinuity values of 0.5±0.2 eV were determined for GaN grown on AlN at 650 °C and 0.8±0.2 eV for GaN grown on AlN at 800 °C. These values are critically evaluated with respect to film quality, the results of other experimental studies, and theory.}, number={4}, journal={JOURNAL OF APPLIED PHYSICS}, author={King, SW and Ronning, C and Davis, RF and Benjamin, MC and Nemanich, RJ}, year={1998}, month={Aug}, pages={2086–2090} }
 @article{dalmer_restle_sebastian_vetter_hofsass_bremser_ronning_davis_wahl_bharuth-ram_1998, title={Lattice site location studies of ion implanted Li-8 in GaN}, volume={84}, ISSN={["1089-7550"]}, DOI={10.1063/1.368463}, abstractNote={The lattice sites of ion implanted Li atoms in GaN were studied as a function of implantation temperature between room temperature and 770 K. We measured the channeling and blocking patterns of α-particles emitted in the radioactive decay of implanted Li8 ions to determine the Li lattice sites. Below 700 K Li atoms occupy mainly interstitial sites in the center of the c-axis hexagons at positions c/4 and 3c/4, where c is the lattice constant in c-axis direction. Around 700 K Li starts to diffuse and presumably interacts with vacancies created in the implantation process. This leads to the formation of substitutional Li above 700 K. An activation energy of about 1.7 eV for interstitial Li diffusion was determined.}, number={6}, journal={JOURNAL OF APPLIED PHYSICS}, author={Dalmer, M and Restle, M and Sebastian, M and Vetter, U and Hofsass, H and Bremser, MD and Ronning, C and Davis, RF and Wahl, U and Bharuth-Ram, K}, year={1998}, month={Sep}, pages={3085–3089} }
 @article{ronning_carlson_thomson_davis_1998, title={Optical activation of Be implanted into GaN}, volume={73}, ISSN={["0003-6951"]}, DOI={10.1063/1.122225}, abstractNote={Single crystalline (0001) gallium nitride layers were implanted with beryllium. Photoluminescence (PL) measurements were subsequently performed as a function of implantation dose and annealing temperature. One new line in the PL spectra at 3.35 eV provided strong evidence for the presence of optically active Be acceptors and has been assigned to band–acceptor (eA) recombinations. The determined ionization energy of 150±10 meV confirmed that isolated Be has the most shallow acceptor level in GaN. Co-implantation of nitrogen did not enhance the activation of the Be acceptors.}, number={12}, journal={APPLIED PHYSICS LETTERS}, author={Ronning, C and Carlson, EP and Thomson, DB and Davis, RF}, year={1998}, month={Sep}, pages={1622–1624} }
 @article{ronning_banks_mccarson_schlesser_sitar_davis_ward_nemanich_1998, title={Structural and electronic properties of boron nitride thin films containing silicon}, volume={84}, ISSN={["0021-8979"]}, DOI={10.1063/1.368752}, abstractNote={The incorporation of silicon into boron nitride films (BN:Si) has been achieved during ion beam assisted deposition growth. A gradual change from cubic boron nitride (c-BN) to hexagonal boron nitride (h-BN) was observed with increasing silicon concentration. Ultraviolet photoelectron spectroscopy, field emission, and field emission electron energy distribution experiments indicated that the observed electron transport and emission were due to hopping conduction between localized states in a band at the Fermi level for the undoped c-BN films and at the band tails of the valence band maximum for the BN:Si films. A negative electron affinity was observed for undoped c-BN films; this phenomenon disappeared upon silicon doping due to the transformation to h-BN. No shift of the Fermi level was observed in any BN:Si film; thus, n-type doping can be excluded.}, number={9}, journal={JOURNAL OF APPLIED PHYSICS}, author={Ronning, C and Banks, AD and McCarson, BL and Schlesser, R and Sitar, Z and Davis, RF and Ward, BL and Nemanich, RJ}, year={1998}, month={Nov}, pages={5046–5051} }
 @article{king_ronning_davis_busby_nemanich_1998, title={X-ray photoelectron diffraction from (3X3) and (root 3X root 3)R30 degrees (001)(Si) 6H-SiC surfaces}, volume={84}, ISSN={["1089-7550"]}, DOI={10.1063/1.368879}, abstractNote={High-resolution (±1°) x-ray photoelectron diffraction (XPD) patterns were obtained along high symmetry azimuths of the (3×3) and (√3×√3)R30° reconstructed (0001)Si 6H–SiC surfaces. The data were compared to XPD patterns obtained from (7×7) Si (111) as well as to models proposed for the (3×3) and (√3×√3)R30° 6H–SiC reconstructions. Forward scattering features similar to those observed from the (7×7) Si (111) were also observed from the (√3×√3)R30° 6H–SiC (0001)Si surface. Additional structures were found and attributed to the substitution of carbon atoms for silicon. Unlike (1×1) and (7×7) Si (111) surfaces, the XPD patterns of (3×3) and (√3×√3)R30° SiC (0001)Si surfaces are different which is due to the presence of an incomplete bilayer of Si on the (3×3) surface. The most significant difference with the Si system is the equivalence of the [101̄0] and [011̄0] azimuths in the (3×3) structure. These results are consistent with a faulted Si bilayer stacking sequence which was proposed based on scanning tunneling microscopy observations.}, number={11}, journal={JOURNAL OF APPLIED PHYSICS}, author={King, SW and Ronning, C and Davis, RF and Busby, RS and Nemanich, RJ}, year={1998}, month={Dec}, pages={6042–6048} }