Regensburg 2016 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 62: Gallium Nitride: Optical and Electronic Properties

HL 62.1: Vortrag

Mittwoch, 9. März 2016, 14:45–15:00, H17

Charge carrier localization in submonolayer InN/GaN superlattices — •Felix Feix, Timur Flissikowski, Caroline Chèze, Raffaella Calarco, Holger T. Grahn, and Oliver Brandt — Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5–7, 10117 Berlin, Germany

The inevitable compositional fluctuations in the random alloy (In,Ga)N lead to the localization of charge carriers with profound implications for their recombination dynamics. Digital alloys composed of an InN/GaN short-period superlattice (SPSL) are envisioned to eliminate alloy disorder and the resulting localization phenomena. However, a recent microscopic investigation of such structures demonstrated that the nominal InN monolayers (ML) in the SPSL have a coverage well below 100 %. Here, we use molecular beam epitaxy to fabricate sub-ML InN/m-ML-GaN superlattices with m = 6 … 44 MLs and investigate these structures by temperature-dependent photoluminescence (PL) spectroscopy under both continuous-wave and pulsed excitation. Both the peak energy and the linewidth of the emission band associated to the sub-ML InN wells exhibit an anomalous dependence on temperature indicative of carrier localization. Delocalization is accompanied by a thermally activated quenching of the emission. PL transients reveal a power law decay at low temperatures reflecting that recombining electrons and holes occupy spatially separate, individual potential minima reminescent of conventional (In,Ga)N quantum wells. These results suggest that essentially the sub-ML InN wells act electronically as two-dimensional random alloys.