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) , 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 [1 10]-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.

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The characteristics of single‐crystal GaN regions obtained by selective‐area and subsequent lateral overgrowth on stripe‐patterned GaAs (001) substrates by MOVPE were studied. Under certain growth conditions, the surface kinetics of the MOVPE process result in lateral‐growth of both hexagonal‐GaN (h‐GaN) and cubic‐GaN (c‐GaN) stripes with the appropriate mask stripe orientation, namely [110] and [1$ \bar 1 $0], respectively. The facet structure comprises the c‐GaN stripes surrounded with (111) B facets and mixture facets of (311) A, (111) A, and an inversed (111) B for the stripe window opening along the [110] and [1$ \bar 1 $0] directions, respectively. The cross‐sectional TEM micrographs showed that the h‐GaN is laterally overgrown along the (111) B facets of the c‐GaN stripes. For the [110]‐stripes, the laterally overgrown h‐GaN regions contained a very low density of dislocations (<108 cm—2). On the other hand, for the [1$ \bar 1 $0]‐stripes, a large reduction of stacking fault density was found in the overgrown c‐GaN regions. We demonstrated that both high quality h‐GaN and c‐GaN films were successfully grown on the stripe‐patterned GaAs (001) substrates by MOVPE.

The metalorganic vapor phase epitaxy (MOVPE) growth of cubic-GaN (c-GaN) layers has been preformed on the [1 1 10]-stripe patterned GaAs (001) substrates. The surface morphology of the laterally overgrown layer was much improved with the formation of the flat (311)A surfaces as the growth proceeded. It is shown that the c-GaN layer thicker than 20 mm was grown on GaAs(001) substrates with the stripe direction in [1 1 10] for 90 min. Microstructure and extended defect distribution in the laterally overgrown c-GaN films have been analysed by transmission electron microscopy (TEM). It is found that the planar defect (stacking faults and twins) density drastically decreases at the region away from the substrate toward the top of the c-GaN stripe. On the other hand, the dislocations become dominant. The density of the dislocations was found to be lower than 10 8 cm --2 . These results suggest that the lateral overgrowth on [1 1 10]-stripe-patterned GaAs (001) substrates via MOVPE is an efficient method for obtaining a low planar defect density c-GaN layer.

We have proposed the use of cubic-GaN (c-GaN) as an intermediate layer for the metalorganic vapor phase epitaxy (MOVPE) growth of hexagonal-GaN (h-GaN) on GaAs (111)B substrates. Insertion of the c-GaN layer at the h-GaN (0001)/GaAs (111) interface significantly improves the crystallinity of the h-GaN layer. Although, we have used [111]-oriented c-GaN layer so far, the lattice-mismatch between h-GaN (0001) and c-GaN (111) is expected to be less than 0.1%, which is much smaller than that for the other commonly used substrate materials. Furthermore, the c-GaN layer was grown at a relatively low growth temperature (T g = 600 °C) to prevent the GaAs substrate from thermal decomposition and to provide a strain relief template layer. This technique enables us to succeed in obtaining nearly strain free h-GaN layers on GaAs (111)B substrates. In this report, the relationship between the nature of the c-GaN intermediate layer and the cubic-to-hexagonal structural transition machanisms are discussed.