Polarization and Space-Charge-Limited Current in III-Nitride Heterostructure Nanowires

An undoped AlGaN/GaN nanowire (NW) demonstrated p-type conductivity solely based on the formation of hole carriers in response to the negative polarization field at the (000-1) AlGaN/GaN facet. A transistor based on this NW displayed a low-voltage transition from ohmic to space-charge-limited conduction. A numerical simulation showed that a highly asymmetric strain exists across the triangular cross section, which creates a doublet peak in the piezoelectric-induced polarization sheet charge at the (000-1) facet. Additionally, there is a strong interplay between the charge at the (000-1) AlGaN/GaN interface with depletion from the three surfaces, as well as an interaction with the opposing polarization fields at two semipolar {- 110-1} facets. The charge distribution and resultant conduction regime is highly interdependent on the configuration of the multilayer structure, and it is not amenable to an analytical model.