© 2014 IEEE. We will review our recent activities on GaAs/AlGaAs electromechanical parametric resonators. Piezoelectric transduction allows us to electrically modulate the resonance frequency, providing an on-chip testbed for nonlinear phononics experiments. Both degenerate and nondegenerate parametric amplification, as well as the excitation of parametric resonance, are performed for single and multi-mode resonators. We demonstrate several nonlinear phenomenon, including phonon lasing, coherent control, phonon propagation switching, and electromechanical signal processing.