A Combination of Ion Implantation and High‐Temperature Annealing: Donor–Acceptor Pairs in Carbon‐Implanted AlN

• Published in: Physica status solidi. A, Applications and materials science Applications and materials science, 2023-08, Vol.220 (16), p.n/a
• Main Authors: Peters, Lukas, Spende, Hendrik, Wolter, Stefan, Margenfeld, Christoph, Ronning, Carsten, Voss, Tobias, Waag, Andreas
• Format: Article
• Language: English
• Subjects: Absorption spectra; AlN; Annealing; Carbon; Cathodoluminescence; Crystal growth; donor–acceptor pair; Free electrons; high-temperature annealing; Impurities; Ion implantation; Low temperature; Oxygen; Temperature dependence
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.202200809

Herein, carbon‐implanted high‐temperature annealed (HTA) AlN layers are analyzed and donor–acceptor pair (DAP) transitions probably between the two most abundant impurities, carbon and oxygen, are identified. Both are regarded as the main, hard‐to‐avoid impurities in crystal growth. Oxygen is believed to lead to absorption in the deep UV below a wavelength of 250 nm. In contrast, carbon is the most likely candidate to be responsible for a distinct absorption band around 265 nm. This interpretation has recently been challenged. In this study, carbon‐implanted and HTA AlN layers with ion fluences above 8.1 × 1015 cm−2 are analyzed using low‐temperature and time‐resolved cathodoluminescence spectroscopy. Due to the high concentration of oxygen inside the AlN, as a result of the HTA process, a DAP transition between a most likely carbon‐related acceptor and ON is observed. The measured temperature‐ and power‐dependent blueshift of the peak emission energy as well as the luminescence transients can be clearly explained by a continuous change from a DAP transition at low temperature to a free electron to acceptor transition with increasing temperature. The findings are supported by a configurational coordinate model that describes the measured behavior qualitatively. A donor–acceptor pair transition in aluminum nitride is identified, probably between the most abundant impurities during crystal growth: carbon and oxygen. High concentrations of both species are realized by ion implantation and diffusion during annealing. The identification is based on continuous‐wave and time‐resolved cathodoluminescence measurements at low and high temperatures plus theoretical considerations.