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Title: Aluminum Nitride-Silicon Carbide Alloy Crystals Grown on SiC Substrates by Sublimation

Abstract

AlN-SiC alloy crystals, with a thickness greater than 500 m, were grown on 4H- and 6H-SiC substrates from a mixture of AlN and SiC powders by the sublimation-recondensation method at 1860-1990 C. On-axis SiC substrates produced a rough surface covered with hexagonal grains, while 6H- and 4H- off-axis SiC substrates with different miscut angles (8? or 3.68?) formed a relatively smooth surface with terraces and steps. The substrate misorientation ensured that the AlN-SiC alloy crystals grew two dimensionally as identified by scanning electron microscopy (SEM). X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed that the AlN-SiC alloys had the wurtzite structure. Electron probe microanalysis (EPMA) and x-ray photoelectron spectroscopy (XPS) demonstrated that the resultant alloy crystals had non-stoichiometric ratios of Al:N and Si:C and a uniform composition throughout the alloy crystal from the interface to the surface. The composition ratio of Al:Si of the alloy crystals changed with the growth temperature, and differed from the original source composition, which was consistent with the results predicted by thermodynamic calculation of the solid-vapor distribution of each element. XPS detected the bonding between Si-C, Si-N, Si-O for the Si 2p spectra. The dislocation density decreased with the growth, which was lower thanmore » 106 cm-2 at the alloy surface, more than two orders of magnitude lower compared to regions close to the crystal/substrate interface, as determined by TEM.« less

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
878275
Report Number(s):
PNNL-SA-47567
9609; KP1303000; TRN: US200611%%9
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: MRS Internet Journal of Nitride Semiconductor Research; Journal Volume: 10; Journal Issue: 5
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINIUM NITRIDES; SILICON CARBIDES; CRYSTAL GROWTH; SUBLIMATION; DISLOCATIONS; SUBSTRATES; THERMODYNAMICS; A2; Growth from vapor; B1; Alloys; B2; Semiconducting materials; Environmental Molecular Sciences Laboratory

Citation Formats

Gu, Zheng, Du, L, Edgar, James H., Payzant, Edward A., Walker, L. R., Liu, R., and Engelhard, Mark H. Aluminum Nitride-Silicon Carbide Alloy Crystals Grown on SiC Substrates by Sublimation. United States: N. p., 2005. Web.
Gu, Zheng, Du, L, Edgar, James H., Payzant, Edward A., Walker, L. R., Liu, R., & Engelhard, Mark H. Aluminum Nitride-Silicon Carbide Alloy Crystals Grown on SiC Substrates by Sublimation. United States.
Gu, Zheng, Du, L, Edgar, James H., Payzant, Edward A., Walker, L. R., Liu, R., and Engelhard, Mark H. Tue . "Aluminum Nitride-Silicon Carbide Alloy Crystals Grown on SiC Substrates by Sublimation". United States. doi:.
@article{osti_878275,
title = {Aluminum Nitride-Silicon Carbide Alloy Crystals Grown on SiC Substrates by Sublimation},
author = {Gu, Zheng and Du, L and Edgar, James H. and Payzant, Edward A. and Walker, L. R. and Liu, R. and Engelhard, Mark H.},
abstractNote = {AlN-SiC alloy crystals, with a thickness greater than 500 m, were grown on 4H- and 6H-SiC substrates from a mixture of AlN and SiC powders by the sublimation-recondensation method at 1860-1990 C. On-axis SiC substrates produced a rough surface covered with hexagonal grains, while 6H- and 4H- off-axis SiC substrates with different miscut angles (8? or 3.68?) formed a relatively smooth surface with terraces and steps. The substrate misorientation ensured that the AlN-SiC alloy crystals grew two dimensionally as identified by scanning electron microscopy (SEM). X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed that the AlN-SiC alloys had the wurtzite structure. Electron probe microanalysis (EPMA) and x-ray photoelectron spectroscopy (XPS) demonstrated that the resultant alloy crystals had non-stoichiometric ratios of Al:N and Si:C and a uniform composition throughout the alloy crystal from the interface to the surface. The composition ratio of Al:Si of the alloy crystals changed with the growth temperature, and differed from the original source composition, which was consistent with the results predicted by thermodynamic calculation of the solid-vapor distribution of each element. XPS detected the bonding between Si-C, Si-N, Si-O for the Si 2p spectra. The dislocation density decreased with the growth, which was lower than 106 cm-2 at the alloy surface, more than two orders of magnitude lower compared to regions close to the crystal/substrate interface, as determined by TEM.},
doi = {},
journal = {MRS Internet Journal of Nitride Semiconductor Research},
number = 5,
volume = 10,
place = {United States},
year = {Tue Dec 20 00:00:00 EST 2005},
month = {Tue Dec 20 00:00:00 EST 2005}
}
  • AlN-SiC alloy crystals, with a thickness greater than 500μm, were grown on 4H- and 6H-SiC substrates from a mixture of AlN and SiC powders by the sublimation-recondensation method at 1860-1990 C. On-axis SiC substrates produced a rough surface covered with hexagonal grains, while 6H- and 4H- off-axis SiC substrates with different miscut angles (8 or 3.68 ) formed a relatively smooth surface with terraces and steps. The substrate misorientation ensured that the AlNSiC alloy crystals grew two dimensionally as identified by scanning electron microscopy (SEM). Xray diffraction (XRD) and transmission electron microscopy (TEM) confirmed that the AlN-SiC alloys had themore » wurtzite structure. Electron probe microanalysis (EPMA) and x-ray photoelectron spectroscopy (XPS) demonstrated that the resultant alloy crystals had non-stoichiometric ratios of Al:N and Si:C and a uniform composition throughout the alloy crystal from the interface to the surface. The composition ratio of Al:Si of the alloy crystals changed with the growth temperature, and differed from the original source composition, which was consistent with the results predicted by thermodynamic calculation of the solid-vapor distribution of each element. XPS detected the bonding between Si-C, Si-N, Si-O for the Si 2p spectra. The dislocation density decreased with the growth, which was lower than 10^6cm-2 at the alloy surface, more than two orders of magnitude lower compared to regions close to the crystal/substrate interface, as determined by TEM.« less
  • Thick (up to 1 mm) AlN-SiC alloy crystals were grown on off-axis Si-face 6H-SiC (0001) substrates by the sublimation-recondensation method from a mixture of AlN and SiC powders at 1860-1990 C in a N2 atmosphere. The color of the crystals changed from clear to dark green with increasing growth temperature. Raman spectroscopy and x-ray diffraction (XRD) confirmed an AlN-SiC alloy was formed with the wurtzite structure and good homogeneity. Three broad peaks were detected in the Raman spectra, with one of those related to an AlN-like and another one to a SiC-like mode, both shifted relative to their usual positionsmore » in the binary compounds, and the third with possible contributions from both AlN and SiC. Scanning Auger microanalysis (SAM) and electron probe microanalysis (EPMA) demonstrated the alloy crystals had an approximate composition of (AlN)0.75(SiC)0.25 with a stoichiometric ratio of Al:N and Si:C. The substrate misorientation ensured a two-dimensional growth mode confirmed by scanning electron microscopy (SEM).« less
  • Density of defect states of aluminum nitride (AlN) films deposited by rf magnetron sputtering on <100>-oriented silicon (Si) and 4H-silicon carbide (4H-SiC) have been investigated using the deep-level-transient-spectroscopy technique. The films were grown at room temperature with varying nitrogen flow from 4 to 20 sccm and a constant argon flow of 10 sccm. In general the defect densities of AlN are lower when grown on 4H-SiC substrates than on Si substrates. The observed defect levels are identified as donor-like triplet of nitrogen vacancy and DX-like centers. Defects located at 0.35-0.42 eV below the conduction band, attributed to dangling bonds ofmore » nitrogen atoms, are seen in samples grown with higher nitrogen flow rate. Shallow level defects, observed at approximately 0.1 eV below the conduction band, can be attributed to the recently discovered prismatic staking fault in the AlN atomic structure.« less
  • 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 {approx}5 x 106/mm2 for those grown directly on SiC substrates to less than 1 x 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 andmore » 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.« less