Current mapping of nonpolar a-plane and polar c-plane GaN films by conductive atomic force microscopy

• The off-axis planes are more electrically active than c-plane and a-plane GaN.
• The C-AFM value in triangular pit is much smaller than that of V-defect.
• Most of the TDs in a-plane GaN have a much lower electrical activity.

Nonpolar (11-20) a-plane GaN and polar (0001) c-plane GaN films have been grown by metal organic chemical vapor deposition on r-plane (1-102) and c-plane (0001) sapphire substrates, respectively. Conductive atomic force microscopy (C-AFM) has been used to investigate the local conductivity of the films. C-AFM shows enhanced current conduction within the etch pits of c-plane GaN and triangular pits of a-plane GaN. The results indicate that the off-axis planes are more electrically active than c-plane and a-plane. Surprisingly, the C-AFM values in triangular pit of the a-plane GaN are much smaller than that in etch pits of the c-plane GaN. The dislocations type related current leakage mechanism is revealed for polar c-plane and nonpolar a-plane GaN films.