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SUMMARY:Network structures in green-emitting InGaN/GaN quantum wells - Nic
 ole van der Laak\, Department of Materials Science and Metallurgy\, Univer
 sity of Cambridge
DTSTART:20060502T140000Z
DTEND:20060502T150000Z
UID:TALK4882@talks.cam.ac.uk
CONTACT:Edmund Ward
DESCRIPTION:The mechanisms operating in green-emitting InGaN/GaN quantum w
 ell\n(QW) structures to give bright luminescence have been the subject of\
 nmuch debate in recent years.  For example\, there have been a vast\nnumbe
 r of investigations performed to determine whether indium\nclustering in I
 nGaN QWs is a valid mechanism for exciton\nconfinement.  Despite these eff
 orts\, conclusive evidence for or\nagainst indium nano-clustering have yet
  to be proven.  More recently\,\nsubstantially higher optical efficiency h
 as been observed for\ncommercial green LED structures which exhibit long-r
 ange thickness\nfluctuations\, compared with LEDs that have uniform InGaN 
 layers.  It\nhas been suggested that these thickness fluctuations may be a
  key to\nquantum confinement.  However\, for this assumption to be valid\,
  it\nmust be assumed that the disk-like regions of InGaN exist\, and that\
 nthe number density of these regions must be higher than the\ndislocation 
 density.\n\nSimilar thickness variations have also been observed in Cambri
 dge-\ngrown InGaN/GaN quantum wells.  Using AFM and several TEM techniques
 \,\nthe actual structure responsible for the observed well-width\nfluctuat
 ions has been determined\, while the variation in the indium\ncomposition 
 and the positions of the threading dislocations relative\nto the QW struct
 ure has also been examined.  This presentation will\nexplore these results
  and outline a possible new mechanism which may\nexplain the bright lumine
 scence observed for green-emitting InGaN QWs.
LOCATION:T001 [Tower Seminar Room]\, Materials Science and Metallurgy\, De
 partment of
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