Material Science Seminar

Dr Matthew Halsall,
School of Electrical and Electronic Engineering,
The University of Manchester,
UK.Visible and Infrared spectroscopy of nitride quantum wells and dotsABSTRACTThe speaker will describe some his recent research concerning the optical properties of semiconductor quantum wells and dots based on the wide gap Al/Ga/In nitride materials. Indium rich InGaN quantum dots have been grown on GaN by MOVPE and studied by AFM. The dots occur at low surface densities, are typically 20-30nm in diameter and 5nm in height, and they also have tendency to occur in closely spaced pairs. Macro and micro photoluminescence studies of these dots show emission due to the dots in the 2.5-2.9eV region of the spectrum and the presence of sharp spectral lines demonstrates the 1D nature of their electronic energy levels. The dot PL linewidth also show the effects of spectral diffusion due to the charging of defect levels in the underlying "wetting layer". The use of Schottky junctions to deplete the impurity levels and reduce this linewidth is discussed. After depletion in this way, the power dependent PL of individual dots reveals a complex energy spectrum dominated by the internal fields present in these wurtzite systems. Finally some recent results on near/mid infrared intersuband structures grown in the AlGaN/GaN system will be presented. These include first mid-infrared Quantum well infrared photoresponse in the 2-5micron region of the spectrum from a device fabricated in this system.September 15th, 2006
2:30-3:50 PM
(Refreshments will be served at 2:15 PM)
SLH 102**All first year materials science majors are required to attend**

Location: John Stauffer Science Lecture Hall (SLH) - 102

Audiences: Everyone Is Invited

Contact: Petra Pearce