Impact of silicon incorporation on the formation of structural defects in AlN
- Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall 3, D-85748 Garching (Germany)
The impact of Si impurities on the structural properties of AlN, grown by plasma-assisted molecular-beam epitaxy on c-plane sapphire is studied. Under nitrogen-rich growth conditions silicon can be homogeneously incorporated up to Si concentrations of [Si]=5.2x10{sup 21} cm{sup -3}. The presence of silicon on the surface during the growth process is demonstrated to be beneficial for the surface morphology and the structural properties of the AlN films. For [Si] up to (5{+-}3)x10{sup 20} cm{sup -3}, this surfactant behavior results in a decrease of the surface roughness from 8 nm for undoped layers grown in a nitrogen-rich regime to less than 1 nm. In addition, high resolution x-ray diffraction studies reveal an increase of the average lateral crystal size from 300 nm to more than 1 {mu}m and a simultaneous decrease of the screw dislocation density from 3.8x10{sup 8} cm{sup -2} for (comparably) weakly doped samples to 2x10{sup 7} cm{sup -2}. At the same [Si] the heterogeneous stress shows a minimum of less than 50 MPa and drastically increases for higher [Si]. The analysis of edge dislocations as a function of [Si] reveals that their density is directly related to Si-induced compressive biaxial stress which increases up to (2.0{+-}0.15) GPa, independently determined by x-ray diffraction and Raman spectroscopy. While edge dislocations are found to be strongly correlated with the release of stress, screw dislocations are formed due to the coalescence of AlN islands with different stacking order, as their density is decreasing with increasing lateral crystal size. For AlN films with [Si]<1.2x10{sup 21} cm{sup -3}, a Poisson ratio {nu}=0.525{+-}0.022 is determined.
- OSTI ID:
- 20884910
- Journal Information:
- Journal of Applied Physics, Vol. 100, Issue 11; Other Information: DOI: 10.1063/1.2363239; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALUMINIUM NITRIDES
DOPED MATERIALS
EDGE DISLOCATIONS
MOLECULAR BEAM EPITAXY
MORPHOLOGY
NITROGEN
POISSON RATIO
PRESSURE DEPENDENCE
PRESSURE RANGE GIGA PA
PRESSURE RANGE MEGA PA 10-100
RAMAN SPECTRA
RAMAN SPECTROSCOPY
RESIDUAL STRESSES
ROUGHNESS
SAPPHIRE
SCREW DISLOCATIONS
SEMICONDUCTOR MATERIALS
SILICON
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION