Helicon-wave-excited plasma nitridation of GaAs after short-time plasma oxidation for fabrication of damage-free GaN/GaAs interface

Short-time (5-30 min) and long-time (5-7 h) helicon-excited (HWP) N2-Ar plasma treatments of GaAs (100) substrates were performed after short-time inductively coupled (ICP) O2-Ar plasmas pretreatments, under two processing conditions in which the plasma sheath widths were small and the largest in our plasma apparatus. The detrimental effects of Ar etching during processing, such as plasma-induced damage, could be reduced if the plasma sheath width was larger. For short-time HWP N2-Ar plasma treatment with the small plasma-sheath width, the effective Schottky barrier height decreased and the reverse leakage current substantially increased with the plasma-exposure time, suggesting the introduction of a high density of the plasma-induced defect centers. On the other hand, the effective barrier height did not change and the reverse leakage current decreased for the GaAs samples treated in HWP N2-Ar plasma with the largest plasma-sheath width. Reasonably good MIS C-V characteristics were obtained for the long-time HWP N2-Ar plasma treatment with the largest sheath width.