Epitaxial lateral overgrowth of GaN by the sublimation method and by MOCVD

Abstract

Selective overgrowth method has been sued to grow GaN epitaxial layers by metalorganic chemical vapor deposition (MOCVD) and sublimation technology. MgO, Si and SiO<SUB>2</SUB> which have different thermal conductivities and thermal expansion coefficients, have been chosen as mask materials. The microstructure and selectively grown GaN and the lateral growth mechanisms of sublimation and MOCVD have also ben investigated by transmission electron microscopy and scanning electron microscopy. The effect of different mask materials on reduction of dislocation density is discussed. The experimental results indicate that Si is the best mask material for GaN lateral overgrowth. The dislocation density is about 10<SUP>9</SUP> cm<SUP>-2</SUP> above the window areas, and it is reduced to 10<SUP>6</SUP> cm<SUP>-2</SUP> in the lateral overgrowth region above the Si mask.