Active slot waveguides were fabricated by embedding low-index Er/Yb silicate material in high-index silicon. A 1.7 dB signal enhancement at 1.53 µm in a 6 mm-long slot waveguide was observed through 1476 nm pumping. The peak Er emission cross-section is determined as 7.53×10(-21) cm2 and the excited Er ion fraction is 0.17. Our experiment shows that the defects in upper c-Si of Si-on-insulator (SOI) and deposited α-Si distorts photoluminescence spectrum and prevents further optical amplification. This negative effect can be partly corrected through annealing treatment, which allows better propagation of the pump light, therefore, stronger excitation in the sandwiched Er/Yb silicate. The defects also affect the 1.53 µm decay curve and are the dominant lifetime reduction mechanism in the active slot waveguide.