Dislocation density reduction via lateral epitaxy in selectively grown GaN structures

Abstract

The microstructure and the lateral epitaxy mechanism of formation of homoepitaxially and selectively grown GaN structures within windows in ${\mathrm{SiO}}_{\mathrm{2}}$ 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 ${\mathrm{SiO}}_{\mathrm{2}}$ mask provided the crystallographic template for the initial vertical growth of the GaN hexagonal pyramids or striped pattern. The ${\mathrm{SiO}}_{\mathrm{2}}$ 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 ${\mathrm{SiO}}_{\mathrm{2}}$ mask. In many of these areas no dislocations were observed.