Mechanisms of dislocation reduction in GaN using an intermediate temperature interlayer Page: 2 of 12
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It is well known that GaN grown on sapphire contains a high density of threading
dislocations in the range of 109 to 1010/cm2 due to the large difference of the lattice
constants and the thermal expansion coefficients between GaN and sapphire. Threading
dislocations have been found to act as non-radiative centers and scattering centers in
electron transport that is detrimental to the performance of light emitting diodes and field
effect transistors 1. Efforts around the world are aimed at reducing the density of
structural defects in GaN. The most successful techniques to date are the epitaxial lateral
overgrowth techniques (ELO). Many studies have focused on understanding the
mechanisms of dislocation reduction using this technique2- 6. In the ELO process, a
dielectric mask is deposited on a first GaN layer. Lithographic techniques are used to
open patterns in the mask. Then, growth of GaN is resumed, nucleation of growth occurs
in the openings and, with the proper growth conditions, lateral growth above the mask
allows the selected epitaxial areas to fully coalesce. Dislocations do propagate through
the openings but bend over the mask where the growth is predominantly lateral. A
number of devices with improved performance have been produced using the ELO
The use of pendeo-epitaxy has also resulted in production of more performant
devices 7-9. In pendeo-epitaxy, lateral overgrowth is initiated on etched GaN mesas.
Similarly to the standard ELO technique, dislocations propagate above the seed areas but
bend over due to lateral growth in the pendeo area.
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Bourret-Courchesne, E.D.; Yu, K.M.; Benamara, M.; Liliental-Weber, Z. & Washburn, J. Mechanisms of dislocation reduction in GaN using an intermediate temperature interlayer, article, April 2, 2001; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc715407/m1/2/: accessed October 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.