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HL: Fachverband Halbleiterphysik

HL 98: Nitrides: Bulk material, films, surfaces and quantum wells

HL 98.7: Vortrag

Freitag, 20. März 2015, 11:15–11:30, EW 201

Molecular beam epitaxy of GaN quantum dots — •Christopher Hein¹, Andreas Kraus¹, Heiko Bremers¹, Fedor Alexej Ketzer¹, Kamran Forghani², Uwe Rossow¹, Ferdinand Scholz², and Andreas Hangleiter¹ — ¹Institute of Applied Physics, TU Braunschweig, Germany — ²Institute of Optoelectronics, Universität Ulm, Germany

Quantum dots are desired nanostructures for laser diodes and non classical light generation. The III-nitride material system constitutes a valuable material for such applications due to their high bandgap and thermal stability. Our samples are grown in a RIBER 32P molecular beam epitaxy system in Stranski-Krastanov self assembled growth. Templates are c-oriented 300µm sapphire substrates on top of which MOVPE GaN (2.5µm) or AlN (500nm) is grown. Our experiments cover temperature dependent (675-725^∘C) deposition and subsequent characterization of uncapped and capped GaN QD. Growth on MOVPE GaN started with a 100 nm tick AlN (700^∘C) buffer. Afterwards 2 min GaN was deposited during which in situ RHEED developed from streaky to a dotty pattern, indicative for Stranski-Krastanov growth. AFM of the samples showed dots with 1.4 nm (700^∘C) up to 2 nm height with densities ranging from 1.3· 10¹⁰/cm² (725^∘C) up to 6.0· 10¹⁰/cm² (675^∘C). At higher temperatures dots reorganize in a way such that smaller dots coalesce due to higher mobility thus reducing the overall density. The QD sample grown at 700^∘C was reproduced on MOVPE AlN and capped with a 30 nm AlN layer to allow for optical characterization.