Overgrowth and characterization of (11-22) semi-polar GaN on (113) silicon with a two-step method

A two-step approach has been developed for the growth of semi-polar (11-22) GaN on patterned (113) silicon substrates, which effectively eliminates Ga melt-back etching at a high temperature, one of the most challenging issues. A (113) Si substrate is patterned into groove trenches by means of using a standard photolithography technique and then anisotropic chemical etching, forming (111) facets with an inclination angle of 58 degrees with respect to c-axis in addition to the un-etched (113) facets. A thick AlN layer is subsequently epitaxially grown on the patterned silicon to cover all the facets ensuring to eliminate the melt-back, followed by selectively depositing SiO2 masks on the (113) facets only. Further GaN overgrowth is performed only on the exposed (111) facets, forming (11-22) semi-polar GaN with high crystal quality along the vertical direction. Stimulated emission at room temperature has been observed with a low threshold. Low-temperature photoluminescence measurements confirm a significant reduction in basal stacking faults density. This method provides a promising approach to effectively suppress the Ga melt-back etching issue, which is particularly important for Al(Ga)N growth on semi-polar GaN that requires a high growth temperature. The presented results are crucially important for developing monolithic on-chip integration of electronics and photonics on silicon.