Point defect evolution in low-temperature MOCVD growth of InN

We present a systematic study of the influence of the growth temperature on the point defect landscape in metal-organic chemical vapor deposition (MOCVD) InN. State-of-the-art InN layers were grown at temperatures from 500 to 550 degrees C and positron annihilation spectroscopy has been used to investigate the incorporation of vacancy defects during the growth process. We find that a decrease of the growth temperature below 550 degrees C leads to increasing free carrier concentrations and lower mobilities. At the same time, positron measurements observe an enhanced introduction of mixed In-N vacancy complexes which gather preferentially at the interface between the InN layer and the GaN template. As the measured In vacancy concentration seems too low to promote efficient defect complexing, it suggests an increased formation of N vacancies at low temperature growth through insufficient cracking of NH3, which may be responsible for the observed increase in the free carrier concentration. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim