RBS analysis of InGaN/GaN quantum wells for hybrid structures with efficient Foerster coupling

There is strong current interest in Foerster resonant energy transfer (FRET) from a semiconductor quantum well (QW) to an overlayer of another luminescent material. The FRET process becomes efficient when the two materials are placed at interaction distance of a few nanometres. The additional requirement of large spectral overlap between the energy donor and acceptor can be satisfied by combinations of InGaN/GaN QWs (as donors) and overlayers of either light-emitting polymers or nanocrystalline semiconductor quantum dots (as acceptors), both of which can be tailored to have high absorption in the QW emission region. Here we study a set of custom grown InGaN/GaN single QW samples, in which the GaN cap layer thickness was varied to modulate the FRET rate in hybrid structures. We used high-resolution grazing angle RBS experiments to determine the GaN cap layer thickness, varied from 2 to 12 nm, which controlled the interaction distance between the QW and the coupled luminescent medium in hybrid structures. The very careful experiments and data analysis are discussed in detail, including a consideration of the errors in the final results obtained. An example of the use of the measured thickness values to confirm the dominance of sheet-to-sheet dipole-dipole interactions in QW-polymer hybrid structures is discussed