In the growing field of wide- and ultra-wide bandgap semiconductors, beta gallium oxide (β-Ga2O3) has emerged as a frontrunner due to its ease of n-type doping, high breakdown strength, and the existence of melt-grown substrates. For n-type doping, silicon has emerged as the dopant of choice, which can be introduced either in situ during growth or by ion implantation. Ion implantation offers advantages for device applications, including selective area doping, but requires thermal annealing to recover implant-induced damage and activate dopants. In addition to the monoclinic β-phase, numerous other polymorphs exist and are often observed as defect inclusions, such as the defect-spinel $\gamma$-phase, which has been observed to form from the β-phase in damaged regions after ion implantation. Understanding the transformations between these phases is important for developing device quality materials and presents unique kinetic questions to explore. In this study, we developed an understanding of dopant activation over a range of implant concentrations, the stability of doping levels with thermal annealing, and the transformation from $\gamma$- to β-phase and its role in the activation of ion implanted films. Mechanisms of dopant activation, and subsequent deactivation, were explored with thermal annealing in a UHV-compatible quartz tube furnace as functions of ambient, temperature, and time. Unintentionally doped homoepitaxial β-Ga2O3 films (400-500 nm) were grown on semi-insulating (Fe-doped) substrates. Silicon was ion implanted at multiple energies to create 100 nm box profiles with target concentrations from 5×1018 to 1×1020 cm-3. With careful control of PH2O and PO2 in the annealing ambient, implanted carriers can be activated to at least 80% after a 950 °C anneal for 5-10 minutes. The maximum tolerable PO2 is strongly dependent on doping concentration and must be < 10-6 bar for the highest concentrations. 950 °C is sufficiently high to recover implant damage and ionize donors with minimal diffusion. However, the optimal anneal time is doping-dependent with “deactivation” occurring for longer times, leading to the conclusion that high doping levels are metastable. This deactivation is attributed to the formation of gallium vacancies, which are known acceptors. Deactivation rates increase with temperature, doping levels, and PO2, which are all consistent with VGa3- formation; an effective activation energy of 1.6 eV was determined. Structural damage and recovery investigations showed that β-Ga2O3 does not fully amorphize with ion implantation, but rather transforms partially to the $\gamma$-phase while retaining regions of β crystallinity, which rapidly seed lattice recovery with annealing. We hypothesize that the formation of $\gamma$-Ga2O3 occurs due to the near commensurate close-packed oxygen sublattice with $\gamma$-Ga2O3, with structural differences primarily occurring in the cation distribution within the oxygen lattice. To understand the phase formation sequence, we followed the structural evolution of amorphous thin films as a function of temperature and heating rates using millisecond Laser Spike Annealing (LSA). From an as-deposited amorphous film, the $\gamma$-phase nucleates at approximately 600 °C and, with increasing temperature to 1100 °C, transforms continuously to the β-phase with no distinct nucleation step and no two-phase coexistence of $\gamma$ and β. Instead, the conversion more closely resembles an order-disorder transformation. At higher heating rates, or as Al is alloyed with the Ga2O3, direct nucleation of the β-phase is observed. We present models to explain this behavior in terms of diffusion limitations at fast heating rates and modified migration energies in the alloyed system.