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Cracking of GaN Based III-Nitride Heterostructures Grown by MOVPE on (0001)-6H-SiC

During the last years, GaN based III-nitrides have been intensively studied due to their potential applications in both short-wavelength range optoelectronics and high speed, high power electronics. Although notable developments have already been achieved [1] there are still a lot of difficulties to be overcome. One of the problems to be controlled is strain which arises because of a large lattice mismatch between GaN films and the commonly used substrates (sapphire or SiC), additionally strengthened by largely differing thermal expansion coefficients. As a result, nitride heterostructures commonly contain dislocation densities up to 10 cm and more and can sometimes even suffer cracking [2, 3]. As cracks strongly limit the design of laser diodes and therefore should be avoided it is necessary to understand cracking mechanisms.