Properties of highly Cr-doped AlN

摘要

Cr concentrations of ～2 at. % were incorporated into AlN during growth by molecular beam epitaxy. Under optimized conditions, single-phase, insulating AlCrN is produced whose band gap shows a small (0.1-0.2 eV) decrease from the value for undoped AlN (6.2 eV), a decrease in a-plane lattice constant and the introduction of two absorption bands at 3 and 5 eV into the band gap. This material shows ferromagnetism with a Curie temperature above 300 K as judged from the difference in field-cooled and zero-field-cooled magnetization. For nonoptimized growth, second phases of Cr_(2)N and Al_(x)Cr_(y) are produced in the AlN and the material is conducting (～1000 Ω cm) with activation energy for conduction of 0.19 eV and apparent band gap of 5.8 eV.