Electrical transport in GaN nanowires grown by selective epitaxy

The authors report on the electrical transport characteristics of undoped, n-doped, and pn-junction GaN nanowires grown by selective epitaxy on GaN/sapphire substrates. The selective epitaxy is realized by a combination of a patterned Si3N4 mask, which defines the position and diameter of the nanowires, and appropriate growth conditions, which lead to a near one-dimensional growth along the c-direction. They find that the electrical transport in nominally undoped nanowires is dominated by space charge limited conduction, and using a new theory for space charge limited conduction, they extract an electron mobility of ∼400cm2∕Vs and a free carrier concentration of ∼1015–1016cm−3. By controlling the nanowire doping, they observe Ohmic transport for n-doped nanowires and rectifying characteristics for pn-junction nanowires.