Probing interface roughness of the GaAs/Al0.3Ga0.7As multi-quantum-well structures using low-temperature photoluminescence spectra

The optical properties of Metalorganic vapour phase epitaxy (MOVPE) grown GaAs/Al0.3Ga0.7As multi-quantum-well structure have been investigated with the help of both room temperature (300 K) and low temperature (4 K) photoluminescence (PL) technique. The morphology of the grown heterostructure has been evaluated from the cross-sectional transmission electron microscopy (XTEM) measurements. We have observed three distinct PL peaks at 1.5672 eV, 1.6047 eV and 1.677 eV corresponding to the three quantum wells at 4 K which exhibited significant quantum shift due to the confinement of the carriers in the respective quantum wells. The plot of quantum shift as function of well width shows that the shift being largest for the thinnest quantum well. A model is further employed to correlate the interface roughness in terms of the obtained line widths of the PL spectra. From this model, the interface roughness due to the three quantum wells viz. 84 A, 64 A, and 44 A, are 13.17 A, 10.41 A and 8.66 A, respectively.