Vertically faceted lateral overgrowth of GaN on SiC with conducting buffer layers using pulsed metalorganic chemical vapor deposition

Abstract

A “pulsed metalorganic chemical vapor deposition” technique has been developed for lateral overgrowth of GaN thin films on SiC with conducting buffer layers for vertically conducting devices. Growth was carried out at temperatures as low as 950 °C keeping a constant gallium flux while pulsing NH3. We demonstrate that, by varying the NH3 pulse duration, growth morphology can be gradually changed from triangular to rectangular for the lateral overgrowth. Even at a V/III ratio as low as 550, high quality smooth layers with (11̄00) vertical facets were successfully grown with a lateral to vertical growth rate ratio as high as 4:1. Atomic force microscopic measurements show the root-mean-square roughness of the laterally overgrown layers to be 7.0 Å. Scanning thermal microscopy was used to measure a thermal conductivity of 1.7 and 1.5 W/cm K, respectively, for the laterally overgrown film and the GaN deposition in the window region.