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HL: Fachverband Halbleiterphysik
HL 62: Nitrides: Advanced Characterization Techniques
HL 62.1: Vortrag
Mittwoch, 16. März 2011, 15:15–15:30, POT 51
Temperature dependent microscopic energy relaxation in semipolar InGaN SQW imaged by spatio-spectrally-time-resolved cathodoluminescence — •Sebastian Metzner1, Frank Bertram1, Jürgen Christen1, Thomas Wunderer2,3, Frank Lipski2, Stephan Schwaiger2, and Ferdinand Scholz2 — 1Inst. of Exp. Physics, OvG-University Magdeburg — 2Inst. of Optoelectronics, Ulm University — 3Palo Alto Res. Center Inc., USA
We present ps-time- and nm-spatially resolved cathodoluminescence (CL) spectroscopy at 4…300K of semipolar InGaN SQW on top of {11-22} GaN facets of 3D inverse pyramids, which were grown by MOVPE using hexagonal SiO2 masks and selective area overgrowth. The microscopic local differences in strain, polarization fields, In-incorporation, and SQW-thickness result in an extremely complex interaction of relaxation, recombination in energy, space, and time via real space transport of the excited carriers. The CL mapping at 300K reveals a huge spectral shift of SQW emission from the center (380nm) to the ridge (535nm) of the inverse pyramids which is accompanied by a drastically increasing recombination time of 200ps (center) to >10ns (ridge) as observed in microscopic CL lifetime maps. To analyze the nanoscopic kinetic in detail, monochromatic spatio-time-resolved CL linescans and local time-delayed spectra have been recorded giving direct access to the microscopic transport mechanism of excited carriers. Using these techniques, we discuss the temperature dependence of energy relaxation via an efficient spatial transfer of carriers inside the SQW from high energy regions near the center towards the ridge.