Probing the charge state of threading dislocations in indium nitride through advanced atomic force microscopy

Indium nitride (InN) plays an imperative role in continuing the success of III-nitride technology and extending its footprint into new application fields. However, the development of InN-based devices is hindered by the unusually high residual electron concentration in unintentionally-doped InN, whose origin remains unresolved. In this work, pits are observed at regions around the InN island boundaries, which are assigned to threading dislocations (TDs). Since the surface band bending of InN is found to be intrinsically downward, the positive currents detected exclusively at the InN island boundary regions upon applying positive sample bias are leakage currents. This further points to the presence of TDs in these regions, which can act as localized conductive leakage paths. Interestingly, the surface potentials at the InN island boundary regions are found to be 35-45 mV more positive compared to the InN islands. This can be attributed to the presence of positively charged TDs due to the formation of donor-type point defects along their dislocation cores. Hence, TDs in InN can donate electrons and serve as one of the factors contributing to its high n-type conductivity.