Correlation between small polaron tunneling relaxation and donor ionization in Ga2O3

Pulsed laser deposition is employed to fabricate as-grown amorphous and post-growth annealed crystalline beta-Ga2O3 films. The films annealed at temperatures above 600 degrees C are found to exhibit a pure monolithic phase with a bandgap of 4.7 eV. The thermally activated donor ionization and dielectric relaxation of these films are systematically investigated by temperature-dependent DC and AC conductivity measurements, and complex electric modulus analysis. A donor level at similar to 180 meV below the conduction band edge and a small polaron tunneling (SPT) relaxation with an activation energy of similar to 180 meV are observed in the as-grown amorphous Ga2O3 film but not in the monolithic beta-Ga2O3 film. The SPT occurs between donor sites with its thermal relaxation of polarization being associated with the thermal ionization of the donor state. Thermal annealing of the amorphous films removes the 180 meV donors as well the corresponding SPT relaxation.

Automated summary

Pulsed laser deposition was used to fabricate as-grown amorphous and post-growth annealed crystalline beta-Ga2O3 films. The films annealed at temperatures above 600 degrees C exhibited a pure monolithic phase with a large bandgap. The thermally activated donor ionization and dielectric relaxation were investigated in these films, revealing the presence of donor levels and small polaron tunneling relaxation in the as-grown amorphous Ga2O3 film but not in the monolithic beta-Ga2O3 film.