Dislocation density reduction via lateral epitaxy in selectively grown GaN structures

The microstructure and the lateral epitaxy mechanism of formation of homoepitaxially and selectively grown GaN structures within windows in SiO2 masks have been investigated by transmission electron microscopy (TEM) and scanning electron microscopy. The structures were produced by organometallic vapor phase epitaxy for field emission studies. A GaN layer underlying the SiO2 mask provided the crystallographic template for the initial vertical growth of the GaN hexagonal pyramids or striped pattern. The SiO2 film provided an amorphous stage on which lateral growth of the GaN occurred and possibly very limited compliancy in terms of atomic arrangement during the lateral growth and in the accommodation of the mismatch in the coefficients of thermal expansion during cooling. Observations with TEM show a substantial reduction in the dislocation density in the areas of lateral growth of the GaN deposited on the SiO2 mask. In many of these areas no dislocations were observed.