Deep-level transient spectroscopy of low-free-carrier-concentration n-GaN layers grown on freestanding GaN substrates: Dependence on carbon compensation ratio

Electron traps in n-GaN layers with a relatively low-free-carrier-concentration of approximately 1 × 1016 cm−3 were characterized by deep-level transient spectroscopy. Sample layers were grown by metal organic chemical vapor deposition with a thickness of 12 µm on freestanding GaN substrates, and were doped with both silicon and carbon. The measurement results showed a reduction in the density of carbon-related electron traps at an energy level of E C −0.40 eV in GaN on GaN samples, compared with GaN on SiC samples. It was also observed that the doping of carbon significantly suppressed electron traps at E C −0.61 eV, which was associated with the nitrogen antisite. Consequently, the possibility of minimizing all of the electron traps located between E C −0.19 and −0.89 eV in n-GaN was demonstrated by controlling the carbon doping in the nitrogen site.