Temperature-dependent characteristics of GaAs/AlGaAs multiple-quantum-well optical modulators

Transmission versus voltage operating characteristics of a GaAs/AlGaAs multiple-quantum-well light modulator have been measured at temperatures between 4.3 and 290 K. At 4.3 K, the linewidth of the heavy-hole exciton absorption is 1.3 meV, and the modulation ratio is greater than 1000 at a 9-V bias. At room temperature, the exciton resonance is broadened to 5.3 meV by phonon scattering and the maximum modulation ratio is 4.93 at 12 V. The measured temperature and voltage dependence of the exciton absorption energies, linewidths, and intensities have been used with a simple model for the modulator’s optical transmission to calculate the operating characteristics as a function of material quality. The upper limit on the room-temperature transmission modulation ratio is estimated to be 5.4 for a device fabricated from 100 quantum wells of width 100 Å.