1. Effect of substrate misorientation on the concentration of impurities and surface morphology of an epitaxial GaN layer on N-polar GaN substrate by MOVPE.
- Author
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Nagamatsu, Kentaro, Ando, Yuto, Kono, Tsukasa, Cheong, Heajeong, Nitta, Shugo, Honda, Yoshio, Pristovsek, Markus, and Amano, Hiroshi
- Subjects
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SUBSTRATES (Materials science) , *SURFACE morphology , *GALLIUM nitride , *EPITAXIAL layers , *VAPOR phase epitaxial growth - Abstract
Highlights • Low impurities concentration in GaN grown by MOVPE using quartz free reactor. • N-polar GaN atomic steps with double height. • Different off-cut angle N-polar GaN for homo-epitaxial growth. Abstract This study examines the effect of (0 0 0 −1) GaN substrate misorientation on the residual impurities and surface morphology of N-polar GaN grown by metalorganic vapor-phase epitaxy. Carbon, silicon, and oxygen concentrations decreased with increasing GaN substrate misorientation angle, with the lowest impurity concentration achieved for a misorientation angle of 2° toward the m-axis, with 6 × 1015 cm−3 carbon, 6 × 1015 cm−3 silicon, and 4 × 1017 cm−3 oxygen atoms. The oxygen concentration was measured at a depth of 0.5 μm below the wafer surface, and the oxygen concentration decreased with increasing thickness. The incorporation of carbon and oxygen revealed a strong dependence on the misorientation angle. The step distance height of the steps parallel to the [1 1 −2 0] direction (or perpendicular to the [1 −1 0 0] m-direction) was confirmed to be a double-height layer step. This phenomenon indicated that m-direction steps are stable for N-polar growth in GaN. In cases of large misorientation toward the m-axis in of the GaN substrate it was difficult to control the misorientation perpendicular to the nominal direction leading to a-axis direction by wafer bowing at wafer manufacturing. Therefore, step-bunching was generated for each symmetric m-axis due to an increase in the compound's off-angle, thus causing the surface roughness to become large. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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