Stress and Defect Control in GaN Using Low Temperature Interlayers

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Abstract
In organometallic vapor phase epitaxial growth of GaN on sapphire, the role of the low-temperature-deposited interlayers inserted between high-temperature-grown GaN layers was investigated by in situ stress measurement, X-ray diffraction, and transmission electron microscopy. Insertion of a series of low temperature GaN interlayers reduces the density of threading dislocations while simultaneously increasing the tensile stress during growth, ultimately resulting in cracking of the GaN film. Low temperature AlN interlayers were found to be effective in suppressing cracking by reducing tensile stress. The interlayer approach permits tailoring of the film stress to optimize film structure and properties.