PENDEOEPITAXIAL METHODS OF FABRICATING GALLIUM NITRIDE SEMICONDUCTOR LAYERS ON WEAK POSTS, AND GALLIUM NITRIDE SEMICONDUCTOR STRUCTURES FABRICATED THEREBY

摘要

A gallium nitride layer (108) is pendeoepitaxially grown on weak posts (106) on a substrate (102) that are configured to crack due to a thermal expansion coefficient mismatch between the substrate (102) and the gallium nitride layer (108) on the weak posts. Thus, upon cooling, at least some of the weak posts (106) crack, to thereby relieve stress in the gallium nitride semiconductor layer (108). Accordingly, low defect density gallium nitride semiconductor layers (112) may be produced. Moreover, the weak posts can allow relatively easy separation of the substrate from the gallium nitride semiconductor layer to provide a freestanding gallium nitride layer (116). The weak posts may be formed by forming an array of posts in spaced apart staggered relation on the substrate. Alternatively, the posts may have a height to width ratio in excess of 0.5, so that the relatively narrow posts promote cracking upon reduction of the temperature. In another alternative, the posts preferably are less than one micron wide, more preferably less than one half micron wide, regardless of height. In yet another alternative, a post weakening region (902) is formed in the posts, adjacent the substrate.