Regensburg 2007 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 46: Poster 2
HL 46.22: Poster
Thursday, March 29, 2007, 15:00–17:30, Poster A
Time-Resolved Photoluminescence of Nitrogen-Cluster States in Dilute Ga(NAs)/GaAs Heterostructures — •David Köhler1, Kristian Hantke1, Swantje Horst1, Sangam Chatterjee1, Peter J. Klar1, Wolfgang Stolz1, Antonio Polimeni2, Mario Capizzi2, and Wolfgang W. Rühle1 — 1Faculty of Physics and Material Sciences Center, Philipps-Universität Marburg, Renthof 5, D-35032 Marburg, Germany — 2CNISM and Dipartimento di Fisica, Sapienza Universitá di Roma, P. le A. Moro 5, I-00185 Roma, Italy
We measured time-resolved photoluminescence on GaNxAs1−x/GaAs epitaxial layers grown by metal-organic vapour-phase epitaxy (MOVPE). The nitrogen concentration x for the as-gown samples varied between 0.049% and 0.238%. Additionally, the effective nitrogen content of the x=0.111% sample was reduced to 0%≤ xeff≤ 0.111% by post-growth hydrogenation. We find distinct PL signals at lower energies than the band-to-band transition. These are attributed to nitrogen-related cluster states formed below the Γ-like conduction-band edge. Higher nitrogen concentrations lead to a redshift of the CB towards the cluster states that are fixed in energy. Furthermore, we present a profound dependence of the PL rise-time on the transition energy. The cluster states show a very long rise time of the PL intensity whereas a fast PL rise-time is found for the band-to-band transition. Therefore, we attribute the PL features at lower energies to zero-phonon nitrogen-cluster states. This is confirmed by TRPL experiments at various temperatures and excitation densities.