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 Angstrom) 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. (C) 1999 American Institute of Physics. [S0021-8979(99)06604-9].