Nonlinear Optical Effects In GaAs/AlAs Type-II Heterostructures

We report on femtosecond and quasi-steady state nonlinear spectroscopic studies of narrow-well Type-II GaAs/AIAs heterostructures. We observe a large intensity-dependent blue shift of the heavy-hole (HH) exciton absorption peak as well as a concomitant blue shift of the Γ-X indirect luminescence peak. 1 In addition, we describe femtosecond transmission measurements of this Type-II system in which an applied axial electric field has biased the levels into the region of an indirect/direct anti-crossing. 2 The femtosecond absorption spectra show intriguing transient energy shifts of the HH exciton. At high fields we report a transient red-shift while a transient blue shift is observed at low fields. These shifts are discussed in terms of the electric-field-dependent Γ-X splitting.