A theoretical analysis of phase enhancement by resonant Fabry-Perot picture elements in III-V semiconductor spatial light modulators (SLM's) is presented. For 90% reflecting electrodes, a phase modulation of 0.7pi rad is found in transmission when the electro-optic input phase is 0.06pi rad. Implementation of this resonant phase-dominant SLM in a 1.5-microm-thick AlGaAs/GaAs multiple quantum well (MQW) structure is proposed. Field effects and carrier-induced electro-optic effects are suggested for the MQW's.