Study of Edge and Screw Dislocation Density in GaN/Al2O3 Heterostructure

Vladimir Lucian Ene; Doru Dinescu; Iulia Zai; Nikolay Djourelov; Bogdan Stefan Vasile; Andreea Bianca Serban; Victor Leca; Ecaterina Andronescu

doi:10.3390/ma12244205

Study of Edge and Screw Dislocation Density in GaN/Al₂O₃ Heterostructure

Materials (Basel). 2019 Dec 14;12(24):4205. doi: 10.3390/ma12244205.

Authors

Vladimir Lucian Ene^{1

2}, Doru Dinescu^{2

3}, Iulia Zai^{2

4}, Nikolay Djourelov², Bogdan Stefan Vasile¹, Andreea Bianca Serban^{2

3}, Victor Leca², Ecaterina Andronescu¹

Affiliations

¹ Department of Science and Engineering of Oxide Materials and Nanomaterials, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, 060042 Bucharest, Romania.
² Extreme Light Infrastructure-Nuclear Physics (ELI-NP), 'Horia Hulubei' National R&D Institute for Physics and Nuclear Engineering (IFIN-HH), 30 Reactorului Street, 077125 Măgurele, Ilfov, Romania.
³ Doctoral School in Engineering and Applications of Lasers and Accelerators, University Politehnica of Bucharest, 060042 Bucharest, Romania.
⁴ Faculty of Physics, University of Bucharest, 077125 Măgurele, Ilfov, Romania.

Abstract

This study assesses the characteristics (edge and screw dislocation density) of a commercially available GaN/AlN/Al₂O₃ wafer. The heterostructure was evaluated by means of high-resolution X-ray diffraction (HR-XRD), high-resolution transmission electron microscopy (HR-TEM), and Doppler-Broadening Spectroscopy (DBS). The results were mathematically modeled to extract defect densities and defect correlation lengths in the GaN film. The structure of the GaN film, AlN buffer, Al₂O₃ substrate and their growth relationships were determined through HR-TEM. DBS studies were used to determine the effective positron diffusion length of the GaN film. Within the epitaxial layers, defined by a [GaN P 63 m c (0 0 0 2) || P 63 m c AlN (0 0 0 2) || (0 0 0 2) R 3 ¯ c Al₂O₃] relationship, regarding the GaN film, a strong correlation between defect densities, defect correlation lengths, and positron diffusion length was assessed. The defect densities ρ d e = 6.13 × 10¹⁰ cm^-2, ρ d s = 1.36 × 10¹⁰ cm^-2, along with the defect correlation lengths L^e = 155 nm and L^s = 229 nm found in the 289 nm layer of GaN, account for the effective positron diffusion length L_eff~60 nm.

Keywords: defect density; edge/screw defect; epitaxial thin films; gallium nitride; slow positrons.