Comparison of electroabsorption in tensile-strained and lattice-matched GaAs(P)/AlGaAs quantum wells

The performance of tensile-strained GaAsP/AlGaAs multiple-quantum well (MQW) reflection modulators is compared to that of similar lattice-matched GaAs/AlGaAs devices operating in the same wavelength range. The tensile-strained modulators utilize ∼95 Å GaAs0.92P0.08 quantum wells, which are designed to make use of the field-induced merging of electron-to-light-hole (e-lh) and electron-to-heavy-hole (e-hh) excitonic absorption edges achievable in tensile strained wells. Unstrained ∼46 Å GaAs quantum wells yielding similar excitonic gaps are utilized in the lattice-matched devices, but the strained and unstrained modulators are otherwise virtually identical. Room-temperature differential reflection spectra reveal increased modulation depths at low drive voltages in the tensile-strained devices, consistent with electroabsorption enhancements expected in these structures from merging of the elh and ehh transitions.