An advanced CMOS-compatible 300- $\text{mm}$ -wafer silicon-photonics platform is introduced that consists of a silicon layer with eight doping masks, two silicon-nitride layers, three metal and via layers, a dicing trench for smooth edge-coupled facets, and a gain-film trench that enables interaction between the gain material and waveguide layers. The platform was used to demonstrate an electrically-steerable integrated optical phased array powered by an on-chip erbium-doped laser. Lasing with a single-mode output, $30\,\text{dB}$ side-mode-suppression ratio, and $\text{40 mW}$ lasing threshold was shown, and one-dimensional beam steering with a $\text{0.85}^\circ \times \text{0.20}^\circ$ full-width at half-maximum and $\text{30}^\circ /\text{W}$ electrical steering efficiency was demonstrated. This system represents the first demonstration of a rare-earth-doped laser monolithically-integrated with an active CMOS-compatible silicon-on-insulator photonics system.