Crystal Lattice Recovery and Optical Activation of Yb Implanted into β-Ga2O3

Abstract

β-Ga2O3 is an ultra-wide bandgap semiconductor (Eg~4.8 eV) of interest for many applications, including optoelectronics. Undoped Ga2O3 emits light in the UV range that can be tuned to the visible region of the spectrum by rare earth dopants. In this work, we investigate the crystal lattice recovery of (2¯01)-oriented β-Ga2O3 crystals implanted with Yb ions to the fluence of 1 ×1014 at/cm2. Post-implantation annealing at a range of temperature and different atmospheres was used to investigate the β-Ga2O3 crystal structure recovery and optical activation of Yb ions. Ion implantation is a renowned technique used for material doping, but in spite of its many advantages such as the controlled introduction of dopants in concentrations exceeding the solubility limits, it also causes damage to the crystal lattice, which strongly influences the optical response from the material. In this work, post-implantation defects in β-Ga2O3:Yb crystals, their transformation, and the recovery of the crystal lattice after thermal treatment have been investigated by channeling Rutherford backscattering spectrometry (RBS/c) supported by McChasy simulations, and the optical response was tested. It has been shown that post-implantation annealing at temperatures of 700–900 °C results in partial crystal lattice recovery, but it is accompanied by the out-diffusion of Yb ions toward the surface if the annealing temperature and time exceed 800 °C and 10 min, respectively. High-temperature implantation at 500–900 °C strongly limits post-implantation damage to the crystal lattice, but it does not cause the intense luminescence of Yb ions. This suggests that the recovery of the crystal lattice is not a sufficient condition for strong rare-earth photoluminescence at room temperature and that oxygen annealing is beneficial for intense infrared luminescence compared to other tested environments.