Structural transition control of laterally overgrown c-GaN and h-GaN on stripe-patterned GaAs (001) substrates by MOVPE

Growth mechanisms and material quality of the laterally overgrown cubic-phase gallium nitride (c-GaN) and hexagonal-phase gallium nitride (h-GaN) on stripe-patterned GaAs (001) substrates were investigated using transmission electron microscopy (TEM). Investigational results show that h-GaN is only laterally overgrown along the (111)B facets of the c-GaN stripes with the growth direction of (0001)h-GaN//(111)B c-GaN for all the mask stripe orientations. Dislocation density in the laterally overgrown h-GaN regions for the [110]-stripe pattern is reduced to be lower than 10⁴ cm^-2, which is six orders of magnitude smaller than that in the conventionally grown h-GaN films. On the other hand, the laterally overgrown c-GaN with lower planar defect (stacking faults and twins) density presents in the region just above the stripe windows for the [110]-stripe pattern. In addition, a large reduction of planar defect density was found in the laterally overgrown c-GaN regions for the [100] stripe direction. Also, a model is used to describe the cubic-to-hexagonal structural transition in lateral-overgrown GaN on patterned GaAs (001) substrates for the purpose of lower dislocation and lower planar defect densities in the laterally overgrown h-GaN and c-GaN, respectively.