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.