skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: The Effect of Aluminum Nitride-Silicon Carbide Alloy Buffer Layers on the Sublimation Growth of Aluminum Nitride on SiC (0001) Substrates

Abstract

No abstract prepared.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
929845
Report Number(s):
BNL-80409-2008-JA
Journal ID: ISSN 0255-5476; MSFOEP; TRN: US200822%%911
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Science Forum; Journal Volume: 527-529
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINIUM NITRIDES; PHYSICAL VAPOR DEPOSITION; CRYSTAL GROWTH; SILICON CARBIDES; SUBSTRATES; BUFFERS; CATALYTIC EFFECTS; national synchrotron light source

Citation Formats

Gu,Z., Edgar, J., Raghothamachar, B., Dudley, M., Zhuang, D., and Sitar, Z. The Effect of Aluminum Nitride-Silicon Carbide Alloy Buffer Layers on the Sublimation Growth of Aluminum Nitride on SiC (0001) Substrates. United States: N. p., 2006. Web. doi:10.4028/www.scientific.net/MSF.527-529.1497.
Gu,Z., Edgar, J., Raghothamachar, B., Dudley, M., Zhuang, D., & Sitar, Z. The Effect of Aluminum Nitride-Silicon Carbide Alloy Buffer Layers on the Sublimation Growth of Aluminum Nitride on SiC (0001) Substrates. United States. doi:10.4028/www.scientific.net/MSF.527-529.1497.
Gu,Z., Edgar, J., Raghothamachar, B., Dudley, M., Zhuang, D., and Sitar, Z. Sun . "The Effect of Aluminum Nitride-Silicon Carbide Alloy Buffer Layers on the Sublimation Growth of Aluminum Nitride on SiC (0001) Substrates". United States. doi:10.4028/www.scientific.net/MSF.527-529.1497.
@article{osti_929845,
title = {The Effect of Aluminum Nitride-Silicon Carbide Alloy Buffer Layers on the Sublimation Growth of Aluminum Nitride on SiC (0001) Substrates},
author = {Gu,Z. and Edgar, J. and Raghothamachar, B. and Dudley, M. and Zhuang, D. and Sitar, Z.},
abstractNote = {No abstract prepared.},
doi = {10.4028/www.scientific.net/MSF.527-529.1497},
journal = {Materials Science Forum},
number = ,
volume = 527-529,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • 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 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 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
  • 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
  • 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
  • Nitride wide-band-gap semiconductors are used to make high power electronic devices or efficient light sources. The performance of GaN-based devices is directly linked to the initial AlN buffer layer. During the last twenty years of research on nitride growth, only few information on the AlN surface quality have been obtained, mainly by ex-situ characterization techniques. Thanks to a Non Contact Atomic Force Microscope (NC-AFM) connected under ultra high vacuum (UHV) to a dedicated molecular beam epitaxy (MBE) chamber, the surface of AlN(0001) thin films grown on Si(111) and 4H-SiC(0001) substrates has been characterized. These experiments give access to a quantitativemore » determination of the density of screw and edge dislocations at the surface. The layers were also characterized by ex-situ SEM to observe the largest defects such as relaxation dislocations and hillocks. The influence of the growth parameters (substrate temperature, growth speed, III/V ratio) and of the initial substrate preparation on the dislocation density was also investigated. On Si(111), the large in-plane lattice mismatch with AlN(0001) (19%) induces a high dislocation density ranging from 6 to 12×10{sup 10}/cm{sup 2} depending on the growth conditions. On 4H-SiC(0001) (1% mismatch with AlN(0001)), the dislocation density decreases to less than 10{sup 10}/cm{sup 2}, but hillocks appear, depending on the initial SiC(0001) reconstruction. The use of a very low growth rate of 10 nm/h at the beginning of the growth process allows to decrease the dislocation density below 2 × 10{sup 9}/cm{sup 2}.« less