Selective-area growth and characterization of cubic GaN grown by metalorganic vapor phase epitaxy

摘要

Selective-area growth of cubic GaN (c-GaN) layers grown on stripe-patterned GaAs (100) substrates by metalorganic vapor phase epitaxy was investigated. The formation of hexagonal phase was examined along with the growth morphology and the lateral-to-vertical growth ratio of the selective-area grown c-GaN stripes. It is found that the hexagonal phase formation significantly depends on growth parameters, particularly, the growth temperature, direction of the stripe pattern, and fill factor. For the [011]- and [011]-stripe patterns, the volume fraction of the hexagonal phase in the c-GaN layers reduces significantly with increasing fill factor. In contrast, it gradually increases with the fill factor for the [001]-stripe pattern. GaN layers with the highest phase purity containing 85% of the cubic phase can be obtained at low growth temperatures (similar to 900 degrees C) for the [011]-stripe pattern with the smallest fill factor of 0.35. A lower lateral growth rate is observed as compared to that at higher growth temperatures (930-960 degrees C). Further evidence is provided by correlating the cathodoluminescence and photoluminescence to the growth facets. Transmission electron microscopy results confirm that h-GaN is easily constructed on the (111)B facet due to the formation of stacking faults. In practice, the [011]-stripe pattern with a large fill factor of similar to 0.7 can be applied to obtain a selective-area grown c-GaN layer with the highest cubicphase purity. Furthermore, the [011]-stripe pattern has also been considered for SAG of c-GaN at low growth temperature.