The introduction of vacancy-type defects into InN by Mg-doping was studied using

a mono-energetic positron beam. Doppler broadening spectra of the annihilation

radiation were measured for Mg-doped InN (N-polar) grown onto GaN/sapphire

templates using plasma-assisted molecular beam epitaxy. The concentration of Invacancy

(VIn) related defects was high near to the InN/GaN interface, and the

defect-rich region extended from the interface and towards the surface with increasing Mg concentration, [Mg]. Using electrolyte-based capacitance-voltage

analysis, it was determined that the conduction type of InN at low [Mg] (up to

1018/cm3) was still n-type. It became p-type with increasing [Mg] (3 x 1018 to 2 x

1019/cm3), but turned n-type again above 3 x 1019/cm3. The point defects introduced

at the conductivity transition from p-type and n-type were found to be complexes

between In-vacancy (VIn) and N-vacancy clusters, such as VIn(VN)3. Below [Mg] =

4 x 1019/cm3, an observed behaviour of positron annihilation parameters was well

explained by assuming the trapping of positrons by N-vacancy clusters such as

(VN)3. This suggested that, although isolated VN was positively charged, a VN

cluster could be a positron-trapping center because of the increased electron

concentration in the local In-rich region.

Vacancy-Type Defects in Mg-Doped InN Probed by Means of Positron

Annihilation. A.Uedono, H.Nakamori, K.Narita, J.Suzuki, X.Wang, S.B.Che,

Y.Ishitani, A.Yoshikawa, S.Ishibashi: Journal of Applied Physics, 2009, 105[5],

054507