Photoluminescence study of as-grown self-catalyzed GaAs/AlGaAs core-shell nanowires

Abstract

A macro-photoluminescence study of self-catalyzed nanowires, using a specializedsetup for this purpose, has been performed. Several samples were even comparedto single nanowire micro-photoluminescence measurements, on the samesamples, done by other students in the nanowire group at NTNU. The macrophotoluminescence measurements were done by changing parameters such as temperature and excitation power. A 532 nm laser was used to excite the wires and thephotoluminescence was measured by a CCD detector attached to a spectroscope.Using macro-photoluminescence measurements in a qualitative comparison withmeasurements done on single nanowires by micro-photoluminescence spectroscopycan give the researcher a decent understanding of the quality of the sample and itscontributions to photoluminescence. Measurements done in this thesis show probablecontributions from most types of transitions expected in zinc-blende nanowires,consisting of such defects as dense zinc-blende/wurtzite heterostructures, highlytwinned regions, but also from nanowires of higher purity.As nanowires move closer to the realization of e.g. nanowire based solar cells,such macro-photoluminescence measurements will become increasingly importantin deciding the overall quality of the grown structures.