This letter reports a systematic study about the effect of surface stoichiometry induced by inductively coupled plasma (ICP) etching on the ohmic contact to N-face n-GaN. It is found that N-face n-GaN surface has a very high activity towards oxygen adsorption. And it is indispensable to remove GaO_x layer on the N-face n-GaN surface prior to the metal deposition to realize ohmic contact. Moreover, the radio frequency power of the ICP etching and the plasma species greatly affect the surface stoichiometry and the electrical property of the ohmic contact to N-face n-GaN. X-ray photoelectron spectroscopy was implemented to characterize the surface stoichiometry of N-face n-GaN after plasma treatment and reveal the mechanism behind the phenomena. As a result, a non-alloyed ohmic contact to N-face n-GaN has been successfully achieved in a reproducible way.

这封信报道了有关由电感耦合等离子体（ICP）蚀刻引起的表面化学计量对N面n-GaN欧姆接触的影响的系统研究。发现N面n-GaN表面具有非常高的氧吸附活性。而且去除GaO _x必不可少在进行金属沉积之前，先在N面n-GaN表面上形成一层有机硅，以实现欧姆接触。而且，ICP蚀刻的射频功率和等离子体种类极大地影响了表面化学计量和与N面n-GaN的欧姆接触的电学性质。利用X射线光电子能谱表征了等离子体处理后N面n-GaN的表面化学计量，揭示了现象背后的机理。结果，已经以可再现的方式成功地实现了与N面n-GaN的非合金欧姆接触。