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

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 x 10(15) 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 O-N 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.

Automated summary

In this study, carbon-implanted and high-temperature annealed AlN layers were analyzed using cathodoluminescence spectroscopy. Donor-acceptor pair transitions between carbon and oxygen impurities were identified. The presence of oxygen led to absorption in the deep UV range, while carbon was responsible for an absorption band at around 265 nm. The findings were supported by temperature- and power-dependent emission energy shifts and luminescence transients.