Electronic state of Er in sputtered AlN:Er films determined by magnetic measurements.

The optoelectronic and piezoelectric properties of AlN:Er thin films have been of great recent interest for potential device applications. In this work, the focus is on the electronic state of Er in AlN:Er thin films prepared by reactive magnetron sputtering on (001) p-type Si substrate. X-ray diffraction shows that Er doping expands the lattice and the AlN:Er film has preferential c-plane orientation. To determine whether Er in AlN:Er is present as Er metal, Er₂O₃, or Er³⁺ substituting for Al³⁺, detailed measurements and analysis of the temperature dependence (2 K-300 K) of the magnetization M at a fixed magnetic field H along with the M vs. H data at 2K up to H=90 kOe are presented. The presence of Er₂O₃ and Er metal is ruled out since their characteristic magnetic transitions are not observed in the AlN:Er sample. Instead, the observed M vs. T and M vs. H variations are consistent with Er present as Er³⁺ substituting for Al³⁺ in AlN:Er at a concentration x=1.08% in agreement with x=0.94%60.20% determined using x-ray photoelectron spectroscopy (XPS). The larger size of Er³⁺ vs. Al³⁺explains the observed lattice expansion of AlN:Er. [ABSTRACT FROM AUTHOR]