Stable and metastable Si negative-U centers in AlGaN and AlN

Abstract

Electron paramagnetic resonance studies of Si-doped Al x Ga 1-x N (0.79 ≤ x ≤ 1.0) reveal two Si negative-U (or DX) centers, which can be separately observed for x 0.84. We found that for the stable DX center, the energy |E DX | of the negatively charged state DX -, which is also considered as the donor activation energy, abruptly increases with Al content for x ∼ 0.83-1.0 approaching ∼240 meV in AlN, whereas E DX remains to be close to the neutral charge state E d for the metastable DX center (∼11 meV below E d in AlN).