Tailoring of electron and hole energies in strained GaAsP/AlGaAs quantum wells using fluorine impurity induced layer disordering

Abstract : Electroabsorption in GaAs/AlGaAs quantum well (QW) waveguides is known to be strongly polarization dependent. Electro-optic effects for the polarization perpendicular to the layer (which shows a strong light-hole (LH) exciton peak) is negligible for the (100) grown QWs. For polarization parallel to the layers the oscillator strengths of the excitons are smaller due to the presence of both the LH and the heavy-hole (HH) exciton transitions. This necessitates a modification of the quantum wells so that stronger oscillator strengths can be obtained for polarization parallel to the layers. This can be accomplished by introducing a small amount of biaxial tensile strain in coherently grown QWs. The influence of biaxial tensile strain in tailoring the hole energies in GaAs and GaAsP QWs has been reported. When a strained GaAsP is used in a quantum well, due to size quantization, the valence bands move down. This movement is in the same direction incurred by the HH but opposite to that incurred by the LH, due to shear strain.