Optical and structural properties of GaInP/InP quantum wells with strained barriers

The authors report on semiconductor quantum well structures in which the well material is unstrained while the barrier region is under tension. They present optical and structural properties of such a configuration, namely, Ga_xIn_1-xP/InP multiple quantum wells (MQWs) onto heavily S-doped InP (001) substrates. Low temperature optical absorption spectra show several well-defined peaks between 1.42 and 1.46 eV. Peaks at several of the same energies are observed in the photoluminescence spectra. A Kronig-Penney model, modified to include strain effects, has been constructed to interpret these spectra using layer thicknesses and strains determined directly by high-resolution X-ray diffraction as input to the model. Good agreement is found between the observed peaks and calculated transitions in the well, barrier and buffer layers. The temperature dependence of the peak positions follows that of the InP bandgap, as expected from this model. A strong enhancement of the absorption coefficient of the barriers is observed as compared to the bulk material