Impact of residual stress on the structural and optical properties of AlN/sapphire heterostructures grown via MOVPE
Applied Physics A: Materials Science and Processing, cilt.132, sa.9, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 132 Sayı: 9
- Basım Tarihi: 2026
- Doi Numarası: 10.1007/s00339-026-10121-3
- Dergi Adı: Applied Physics A: Materials Science and Processing
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Aerospace Database, Chemical Abstracts Core, Chimica, Compendex, INSPEC, Academic Search Ultimate (EBSCO), Engineering Source (EBSCO), Materials Science & Engineering Collection (ProQuest), Technology Collection (ProQuest)
- Anahtar Kelimeler: AlN/sapphire, HRXRD, MOVPE, Nucleation Layer, Residual stress
- Sivas Cumhuriyet Üniversitesi Adresli: Evet
Özet
Residual stress critically influences the structural quality and reliability of AlN-based deep-UV optoelectronic devices. This study investigates the effect of nucleation layer (NL) temperature on the structural, morphological, optical, and residual stress properties of AlN films grown on sapphire by Metal-Organic Vapor Phase Epitaxy (MOVPE). Strain–stress evolution was evaluated from the in-plane and out-of-plane strains using High-Resolution X-ray Diffraction (HRXRD), while structural and surface morphology were characterized by HRXRD and Atomic Force Microscopy (AFM). Optical properties were assessed by spectrophotometry. A comparative study of AlN films grown at intermediate nucleation layer (NL) temperatures (770–855 °C) and at an optimized NL temperature of 1050 °C reveals a strong correlation between NL growth temperature and the resulting film properties. AlN films grown at NL temperatures of 770–855 °C exhibit a high island density, with RMS roughness values decreasing from 3.1 ± 0.5 to 1.0 ± 0.2 nm and moderate compressive stress (from 0.13 to 1.87 GPa), without significant improvement in crystal quality. Notably, the film grown at 825 °C exhibits a nearly stress-free state (0.13 ± 0.02 GPa), indicating that the residual stress evolution within the intermediate NL temperature regime is not simply monotonic with increasing temperature. Increasing the NL temperature to 1050 °C promotes large coalesced grains with an RMS roughness of 1.3 ± 0.3 nm, superior crystal quality with a RC-(0002) FWHM of 126 arcsec, lower screw dislocation density (3.42 × 10⁷ cm⁻²), and higher compressive stress (4.04 ± 0.03 GPa). Optical analysis shows a slight band-gap widening from 6.12 to 6.14 eV, indicating a limited influence of NL temperature on the optical band-edge properties. The overall compressive stress arises from the thermal mismatch between the AlN layer and the sapphire substrate, together with intrinsic stress related to the deposition conditions. These results highlight the critical role of NL temperature in controlling residual stress and crystalline quality, providing practical guidance for strain engineering in AlN/sapphire templates.