Heavy doped n-type $\beta$-Ga ${}_{\mathrm{2}}$O ${}_{\mathrm{3}}$ (HD-Ga ${}_{\mathrm{2}}$O ${}_{\mathrm{3}}$) was obtained by employing Si ion implantation technology on unintentionally doped $\beta$-Ga ${}_{\mathrm{2}}$O ${}_{\mathrm{3}}$ single crystal substrates. To repair the Ga ${}_{\mathrm{2}}$O ${}_{\mathrm{3}}$ lattice damage and activate the Si after implantation, the implanted substrates were annealed at 950℃, 1000℃, and 1100℃, respectively. High-resolution X-ray diffraction and high-resolution transmission electron microscopy show that the ion-implanted layer has high lattice quality after high-temperature annealing at 1000℃. The minimum specific contact resistance is 9.2×10^–5Ω·cm², which is attributed to the titanium oxide that is formed at the Ti/Ga ${}_{\mathrm{2}}$O ${}_{\mathrm{3}}$ interface via rapid thermal annealing at 480℃. Based on these results, the lateral $\beta$-Ga ${}_{\mathrm{2}}$O ${}_{\mathrm{3}}$ diodes were prepared, and the diodes exhibit high forward current density and low specific on-resistance.