Electrochemical deposition of copper on single-crystal gallium nitride(0001) electrode: nucleation and growth mechanism

• The nucleation and growth of Cu electrodeposition on n-GaN was explored.
• The Cu deposition commenced at a large negative potential of −840 mV vs. Pt/Pt2+.
• The deposition process was quasi-reversible and mass transfer limited.
• The deposition occurred on the conduction band of n-GaN.

The electrodeposition of Cu on n-type single-crystal GaN(0001) electrode from sulfate solution was investigated by electrochemical techniques and scanning electron microscopy. It was found that Cu deposition on GaN(0001) commenced at a large negative potential of −840 mV vs. Pt/Pt2+ and was quasi-reversible and mass transfer limited. On the basis of Tafel plot, a low exchange current density of ∼ 2.3 × 10−6 mA cm−2 was calculated. This was mainly due to the limited free electrons in the conduction band of GaN. In addition, the current transient measurements revealed that the deposition process followed the progressive nucleation in 0.5 M H2SO4 + 5 mM CuSO4. The instantaneous nucleation was observed only at the large applied potential of −1.1 V.