Hydrogen and nitrogen ambient effects on epitaxial lateral overgrowth (ELO) of GaN via Metalorganic Vapro-phase epitaxy (MOVPE)

摘要

Ambient gas effect on the epitaxial lateral overgrowth (ELO) of GaN via metalorganic vapor-phase epitaxy (MOVPE) on a MOVPE-grown GaN (0001)/sapphire (0001) substrate with a SiO(sub)2 stripe mask has been studied by means of field-emission scanning electron microscopy (SEM) and highresolution X-ray diffraction (XRD) analysis. Different ambient gases of nitrogen, hydrogen and their mixture (mixture ratio, hydrogen:nittrogen=1:1) affect the lateral overgrowth rate, the surface morphology and the crystalline tilting of ELO-GaN layers. XRD revealed that the ELO-GaN layer on the SiO(sub)2 mask aligned along the <1100> direction exhibited anisotropic crystalline tilting toward <1120>. For ELLO-GaN growth in nitrogen ambient, the growth rate of the (0001) facet decrease, the lateral overgrowth rate increases and the tilting of the ELO-GaN layer increases, while no smooth surface is obtained. in comparison with ELO-GaN growth in hydrogen ambient. For the mixture ambient, a smooth surface with a fast lateral overgrowth rate is achieved and the dislocation density is not more than 10(sup)7 cm sup -2, which is comparable to that in hydrogen ambient.