Oscillator strength of excitons in (In, Ga)As/GaAs quantum wells in the presence of a large electric field

The oscillator strength of the fundamental heavy-hole exciton in strained quantum well (QW) InxGa1−xAs/GaAs p–i–n diode heterostructures is calculated by using a variational approach combined with the transfer matrix formalism. Unlike the weak well thickness dependence of the excitonic properties in the absence of electric field, a completely different picture is observed as the strength of the built-in electric field increases. A dramatic reduction of the QW oscillator strength is noticed for thick wells over the entire indium composition range. This is thought to be induced by a very effective quantum confined Stark effect that becomes a limiting factor for maximized absorption properties. In contrast, calculations for highly strained (x>0.20) thin (less than 50 Å) structures evidence oscillator strength values as large as those found with zero electric field. Finally, the results of this study stress adequate well thickness/composition selection for improved performance of optoelectronic multiple QW-based devices such as modulators and photoconverters.