Optical and Vibrational Characterizations of AlN:Er Epilayers
T.

1
Kallel ,

M.

1
Dammak ,

J.

2
Wang ,

W. M.

2
Jadwisienczak ,

A.

3
Anders

1. Laboratoire de Physique Appliquée, Groupe de Physique théorique, Université de Sfax, Faculté des Sciences de Sfax,
Départemenet de Physique, Route de Soukra, Km 3.5, B.P. 1171 3000 Sfax, Tunisie
2. School of Electrical Engineering and Computer Science, Ohio University, Athens, OH 45701, USA
3. Lawrence Berkeley National Laboratory, Plasma Applications Group, Berkeley, CA 94720, USA
Kaltarak@yahoo.fr
Abstract:
Two sets of aluminum nitride (AlN) epilayers deposited on sapphire (0001) and silicon (100) substrates by molecular beam epitaxy were implanted with erbium ions at room temperature with an implanted ion fluence of 5.51015 at/cm2 and ion energy range not
exceeding 150 keV. The as-implanted samples were annealed at 1050 C to remove defects and make Er3+ ions optically active. AlN:Er3+ samples were investigated by high resolution cathodoluminescence (CL) and Raman spectroscopy in the 7 K - 300 K
temperature range. The comparison of the CL spectra measured for AlN:Er3+ grown on Sapphire and Silicon substrates shown a great similarity with slightly emission lines shift. In theoretical modeling we assumed that Er3+ ions are involved in substitutional
Al-site. Simulations are carried out using crystal field parameters determined using electrostatic point charge model and crystal field theory. The Er3+ ion emission lines shift observed between CL spectra of AlN:Er3+ grown on sapphire and silicon substrates was
explained by the presence of induced stress in AlN:Er3+ thin films and further studied by Raman spectroscopy. Using Raman scattering at different temperatures, we have shown the presence of the allowed E2(high) and A1(LO) phonon modes in AlN:Er3+
epilayers. The correspondent frequencies are in good agreement with theoretical predictions. It was observed that tensile stress exists in AlN:Er3+ epilayer grown on sapphire in contrast to compressive stress present in the AlN:Er3+ epilayer grown on silicon as
indicated by the observed E2(high) mode frequency shift and the broadening of vibrational linewidth. The stress value was calculated using the linear approximation. The temperature dependence of the E2(high) frequency and the vibrational linewidth show that
the tensile stress in AlN:Er3+ epilayer on sapphire decreases with increased temperature.