Indium segregation in ultra-thin In(Ga)As/GaAs single quantum wells revealed by photoluminescence spectroscopy

A nondestructive approach is described that is applicable for studying the In-segregation phenomena in ultra-thin In(Ga)As/GaAs nanostructures grown by molecular beam epitaxy. The proposed method utilizes only the experimental photoluminescence (PL) spectroscopy data and the effective bandgap simulation of specially designed ultra-thin In(Ga)As/GaAs nanostructures. On the example of InAs and In0.25Ga0.75As quantum wells with thicknesses of 1 monolayer (ML) and 4 MLs, respectively, a good correlation for the In segregation coefficient obtained from the proposed method and STEM (scanning transmission electron microscope) Z-contrast cross section imaging is demonstrated. However, PL has a significant advantage over STEM for being a nondestructive, reliable, and rapid technique for measuring multiple samples or large areas. Furthermore, tuning of In segregation in ultra-thin In(Ga)As/GaAs nanostructures, as well as the possibility of modifying and controlling the In depth-distribution profile by the change of growth temperature or the thickness of the low-temperature GaAs capping layer, are additionally demonstrated. A detailed analysis of indium segregation allows the design and precise growth of ultra-thin In(Ga)As/GaAs nanostructures for lasers, solar cells, and infrared photodetectors.