Field-induced absorption edge merging in tensile strained GaAsP quantum wells

Field-induced merging of electron-to-light-hole (e-lh) and electron-to-heavy-hole (e-hh) excitonic absorption edges in tensile-strained quantum wells is demonstrated for the first time. Photocurrent spectra (77 K) of a GaAs0.92P0.08/Al0.37Ga0.63As multiple-quantum-well structure embedded in a p-i-n diode clearly show reduction and eventual elimination of a zero-bias ∼7 meV splitting between the e-lh and e-hh exciton peaks with increasing reverse bias. The unique ‘‘light-hole-up’’ valence subband configuration required for this field-induced merging is achieved through a combination of tensile strain and quantum-size effects in the ∼95 Å GaAs0.92P0.08/Al0.37Ga0.63As multiple quantum wells. The ability to control and eliminate the splitting between the e-lh and e-hh absorption edges via an applied electric field offers possibilities for improving the performance of electroabsorption modulators.