Schematic of the possible conduction channels in Mg-doped GaInN. (in all the mechanisms the surface layer is n-type degenerate) (a) Bulk layer is p-type. (b) The p-type conductivity occurs in the bulk layer below a certain depth from the surface [20,29]. (c) The p-type conductivity is not within a uniform layer but occurs through p-type percolation channels [30,31].
Balkan et al. Nanoscale Research Letters 2012 7:574 doi:10.1186/1556-276X-7-574