Electrical and optical properties of Fe-doped semi-insulating GaN templates

Electrical and optical properties of semi-insulating GaN films with the lower part of the film doped with Fe were studied. The room-temperature sheet resistivity of the films was found to be 2×1010 Ω/square. The activation energy of the dark conductivity was ∼0.5 eV which corresponds to the depth of the dominant electron traps pinning the Fermi level. The concentration of these traps was highest in the Fe-doped portion of the films and was on the order of 3×1016 cm−3. Photoinduced current transient spectroscopy also showed the presence of a high concentration of deeper electron traps with level at EC−0.9 eV and hole traps at EV+0.9 eV. These layers look very promising as insulating buffers for AlGaN/GaN transistor structures.