Effects of the AlN nucleation layer thickness on the crystal structures of an AlN epilayer grown on the 6H-SiC substrate

ABSTRACT

The influence of the LT-AlN(NL) growth times on the mosaic structure parameters of the AlN layer grown on the LT-AlN(NL)/6H-SiC structures as well as the dislocation densities and the strain behaviours in the AlN epilayers has been investigated using XRD measurements. The growth times of the LT-AlN(NL) were changed to 0, 60, 120, 180, and 240 s. We observed that the mosaic structure parameters of the AlN epilayers were slightly affected by the LT-AlN(NL) growth times. However, the dislocation densities in the AlN layer are affected by the growth times of the LT-AlN(NL) layer. The highest edge dislocation density (5.48 × 10¹⁰ ± 2.3 × 10⁹ cm⁻²) was measured for the sample in which 120 s grown LT-AlN(NL) was used. On the other hand, highest screw type dislocation density (1.21 × 10¹⁰ ± 1.7 × 10⁹ cm⁻²) measured in the sample E that contains 240 s growth LT-AlN(NL). The strain calculation results show that the samples without LT-AlN(NL) suffered maximum compressive in-plane strain (−10.9 × 10⁻³ ± 1.8 × 10⁻⁴), which can be suppressed by increasing the LT-AlN(NL) growth times. The out-of-plane strain also has a compressive character and its values increase with LT-AlN(NL) growth times between 60 and 180 s. Same out-of-plane strain values were measured for the LT-AlN(NL) growth times of 180 and 240 s. Furthermore, the form of the biaxial stress in the AlN epilayer changed from compressive to tensile when the LT-AlN(NL) growth times were greater than 120 s.

KEYWORDS:

• B1. AlN nucleation layer
• A1. Mosaic structures
• A1. High resolution X-ray diffraction
• A3. Metalorganic chemical vapor deposition (MOCVD)

Acknowledgements

This work is supported by TUBITAK under Project No. 116F041. One of the authors (E.O.) also acknowledges partial support from the Turkish Academy of Sciences.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work is supported by TUBITAK under Project No. 116F041. One of the authors (E.O.) also acknowledges partial support from the Turkish Academy of Sciences.