Cathodoluminescence hyperspectral imaging of trench-like defects in InGaN/GaN quantum well structures

Jochen Bruckbauer, Paul R Edwards, Suman-Lata Sahonta, Fabien C-P Massabuau, Menno J Kappers, Colin J Humphreys, Rachel A Oliver, Robert W Martin

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Abstract

Optoelectronic devices based on the III-nitride system exhibit remarkably good optical efficiencies despite suffering from a large density of defects. In this work we use cathodoluminescence (CL) hyperspectral imaging to study InGaN/GaN multiple quantum well (MQW) structures. Different types of trench defects with varying trench width, namely wide or narrow trenches forming closed loops and open loops, are investigated in the same hyperspectral CL measurement. A strong redshift (90 meV) and intensity increase of the MQW emission is demonstrated for regions enclosed by wide trenches, whereas those within narrower trenches only exhibit a small redshift (10 meV) and a slight reduction of intensity compared with the defect-free surrounding area. Transmission electron microscopy (TEM) showed that some trench defects consist of a raised central area, which is caused by an increase of about 40% in the thickness of the InGaN wells. The causes of the changes in luminescences are also discussed in relation to TEM results identifying the underlying structure of the defect. Understanding these defects and their emission characteristics is important for further enhancement and development of light-emitting diodes.
Original languageEnglish
Pages (from-to)135107
Number of pages6
JournalJournal of Physics D: Applied Physics
Volume47
Issue number13
Early online date11 Mar 2014
DOIs
Publication statusPublished - 11 Mar 2014

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Keywords

  • cathodoluminescence
  • hyperspectral imaging
  • trench-like defects
  • nGaN/GaN
  • quantum well structures

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