Where β is the field enhancement factor, Φ is the work function of
the electron emitter, which is estimated to be 4.1 eV for GaN [8].
Whereas A and B are constants with the values of 1.56×
10−10 A V−2 eV and 6.83×103 V eV−3/2 μm−1 respectively. The corresponding
FN [ln (I/V2)−1/V] plot of grass-like GaN nanostructures
has been depicted in the insight of Fig. 3(a).The linear behavior of
semi conducting grass-like GaN at high field reveals that the electron
emission is due to the vacuum and quantum tunneling effect [9,14].