TEM Studies and Contact Resistance of Au/Ni/Ti/Ta-GaN Ohmic Contacts

摘要

Ohmic Ta/Ti/Ni/Au contacts to n-GaN have been studied using high resolution electron microscopy (HREM), energy dispersive X-ray spectrometry (EDX) and electron energy loss spectrometry (EELS). Two different samples were used: A - annealed at 750℃ with contact resistance 5x10~(-6) Ω cm~2 and B - annealed at 775℃ with contact resistance 6x10~(-5) Ω cm~2. Both samples revealed extensive in- and out-diffusion between deposited layers with some consumption of GaN layer and formation of Ti_xTa_(1-x)N_(50)( 0 < x < 25 ) at the GaN interface. Almost an order of magnitude difference in contact resistances can be attributed to structure and chemical bonding of Ti-O layers formed on the contact surfaces.