Date of Award

1-1-2010

Document Type

Campus Access Thesis

Department

Electrical Engineering

First Advisor

Asif Khan

Abstract

III-nitride semiconductors based Deep UV LEDs are the prospective candidates to replace the traditional UV sources, such as mercury vapor lamps, used in the applications of water and air purification, germicidal and biomedical instrumentation systems and others. Due to the lack of native substrates, sapphire is being used most abundantly for growing III-nitride based deep-UV device structures. Due to highly lattice mismatched hetero epitaxial growth of deep-UV structures on sapphire substrates, the efficiency of Deep UV LEDs is greatly reduced. Misfit dislocations originated at the interface between AlN epilayer and sapphire substrate is one of the major problems that needs to be effectively studied and overcome.

A systematic analysis of various defects present in AlN layers grown on sapphire substrate as a part of deep-UV emitter structures will be extremely useful for the improvement of growth procedures and to understand defect formation. The primary aim of this thesis is to focus and analyze the characteristics of AlN grown on (0001) sapphire substrates by using characterization techniques, such as Optical Microscopy, Atomic Force Microscopy (AFM), X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). AlN layers grown by pulsed metal organic vapor deposition (MOCVD) have been used for this analysis. The AlN layers were grown using three different low temperature buffer layer conditions. XRD reciprocal lattice mapping and TEM microstructural analyses have been extensively used to analyze the origin of strain and defects in the AlN layers.

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