Epitaxial Recovery of beta-Ga2O3 after High Dose Implantation

TL;DR

This study investigates the damage and lattice recovery of beta-Ga2O3 films after high-dose Ge ion implantation and thermal annealing, revealing conditions for full epitaxial recovery and phase transformations.

Contribution

It demonstrates the conditions under which beta-Ga2O3 recovers epitaxially after high-dose implantation, including the formation of new phases during annealing.

Findings

Full epitaxial recovery at 900°C for low damage implants

Gamma-phase related peaks diminish with annealing at high temperatures

New diffraction peaks suggest phase transformation from gamma to beta

Abstract

As an ultrawide bandgap semiconductor, beta-Ga2O3 has been attractive for its strong tolerance to irradiation damage and high n-type conductivity through ion implantation. Homoepitaxial (010) \b{eta}-Ga2O3 films grown by MOCVD were implanted with Ge to study the post-implantation damage and lattice recovery after thermal annealing. Box profiles of 100 or 50 nm at concentration of 5*10^19 or 3*10^19 cm^-3 were formed, with maximum displacement per atom (DPA) of 1.2 or 2.0. Lattice recovery was investigated using X-ray diffraction (XRD) for anneals from 100 C to 1050 C. A gamma-phase related peak was observed for all implant conditions. All samples showed strain relaxation of beta-phase peak at temperature below 500 C, with no significant change for the gamma-phase related peak. For lower damage implants, films recovered fully to epitaxial beta-phase after sequential annealing to 900 C. For the higher damage implant, the gamma-phase associated peak annealed out with increasing temperature, but a new diffraction peak formed at slightly smaller lattice spacing; full recovery of the lattice was not observed until annealing at 1050 C. The newly formed diffraction peak is identified as beta-(20-4), beta-(512), or beta-(71-2), each potentially arising from the conversion of gamma-phase to beta-phase via a common oxygen sub-lattice.