Origin of the n-type conductivity of InN:: The role of positively charged dislocations

As-grown InN is known to exhibit high unintentional n-type conductivity. Hall measurements from a range of high-quality single-crystalline epitaxially grown InN films reveal a dramatic reduction in the electron density (from low 10(19) to low 10(17) cm(-3)) with increasing film thickness (from 50 to 12 000 nm). The combination of background donors from impurities and the extreme electron accumulation at InN surfaces is shown to be insufficient to reproduce the measured film thickness dependence of the free-electron density. When positively charged nitrogen vacancies (V-N(+)) along dislocations are also included, agreement is obtained between the calculated and experimental thickness dependence of the free-electron concentration.(c) 2006 American Institute of Physics.