Deep centers in graded-index separate confinement heterostructure single quantum-well laser structures, that had been grown by means of molecular beam epitaxy or metalorganic chemical vapor deposition, were investigated by using deep-level transient spectroscopy. The majority and minority carrier deep-level transient spectra showed that the deep (hole and electron) traps (H1, E3), with large capture cross-sections and concentrations, were observed in the graded n-type GaAlAs layers; in addition to the well-known DX centers. In the case of laser structures which had been grown by means of molecular beam epitaxy, the deep hole trap (H1) and the deep electron trap (E3) could be spatially localized in interface regions of discontinuously varying Al mole fraction in n-type AlxGa1-xAs layers, where x was between 0.20 and 0.43. In the case of laser structures which had been grown by means of metalorganic chemical vapor deposition, the deep electron trap (E3) could be spatially localized in n-type AlxGa1-xAs layers, where x was between 0.18 and 0.30. The DX center could be spatially localized in interface regions of discontinuously varying Al mole fraction in AlxGa1-xAs layers, where x was between 0.22 and 0.30.

L.Lu, S.Feng, J.Xu, H.Yang, Z.Wang, J.Wang, Y.Wang, W.Ge: Journal of Crystal Growth, 1996, 169[4], 643-8