Positron annihilation spectroscopy was used to study vacancy type defects in GaAs based superlattices used for 1.3μm quantum well lasers. The samples were molecular beam epitaxy grown on p-type GaAs substrates. Three sets of samples were used for the experiment. For each set the superlattice structure consisted of 10 periods of the quantum well material separated by a GaAs buffer. Specimens of GaInAs, GaNAs and GaInNAs were used as quantum-well material. The growth temperature was 420C for each sample set and some of the samples were annealed. For annealed samples, it could be shown that vacancies were formed in the superlattice structure or at interface between the GaAs cap and the superlattice structure in the annealing process and that the formation was related to the N content. Annealed GaAsN and GaInAsN superlattice samples were found to contain vacancies, most likely in the Ga sub-lattice.

Nitrogen-Related Vacancy Formation in Annealed GaInNAs Quantum-Well Superlattices. J.Slotte, K.Saarinen, E.M.Pavelescu, T.Hakkarainen, S.Karirinne, T.Jouhti, M.Pessa: Physica B, 2006, 376-377, 857-860