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

Abstract

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 [01¯1]–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 (~ 900°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°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 [01¯1]–stripe pattern with a large fill factor of ~ 0.7 can be applied to obtain a selective–area grown c–GaN layer with the highest cubic-phase purity. Furthermore, the [011]–stripe pattern has also been considered for SAG of c–GaN at low growth temperature.