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- Paskova, Tanja, 1961-, et al.
(författare)
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Defect and emission distributions in bulk GaN grown in polar and nonpolar directions : a comparative analysis
- 2008
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. ; , s. 68940D1-
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Konferensbidrag (refereegranskat)abstract
- We have investigated bulk GaN material grown by HVPE either in the conventional polar [0001] direction and subsequently sliced with nonpolar surfaces or grown in the nonpolar [11-20] direction. Spatially resolved techniques such as cathodoluminescence imaging and transmission electron microscopy, as well as profile measuring techniques such as positron annihilation spectroscopy and secondary ion mass spectroscopy were employed to directly visualize the extended structural defects, and point defect (impurity and vacancy) distributions along the growth axes. A comparative analysis of the results shows a distinctive difference in the distribution of all kind of defects along the growth axes. A significant decrease in the defect density in material grown along the polar direction, in contrast to the constant behavior of the high defect density in material grown along the nonpolar direction points out the low-defect superior quality of the former material and indicates the preferable way of producing high-quality GaN substrates with nonpolar surfaces.
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| 3. |
- Paskova, Tanja, et al.
(författare)
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Polar and nonpolar HVPE GaN substrates: impact of doping on the structural, electrical and optical characteristics
- 2009
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Ingår i: Physica Status Solidi. C, Current topics in solid state physics. - : Wiley. - 1610-1634 .- 1610-1642. ; 6:2, s. 344-347
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Tidskriftsartikel (refereegranskat)abstract
- Polar and nonpolar bulk GaN substrates with low defect density and high structural and optical quality are demonstrated. The effect of doping by silicon, oxygen and iron within moderate doping levels on the properties of the polar GaN substrates was found uncompromised, as confirmed by high resolution X-ray diffraction and low temperature photoluminescence spectroscopy. In contrast, the lattice parameters were affected significantly, which has to be considered in the subsequent homoepitaxial device growth. The boule growth and respectively the nonpolar substrate homogeneity were found to be hampered by the doping, due to surface microcracking and higher impurity incorporation, while n-type undoped nonpolar substrates were demonstrated of superior quality.
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