Si+ Implantation and Activation in GaN Comparison of GaN on Sapphire and GaN on Silicon

In this paper, we evaluated gallium nitride heteroepitaxially grown on sapphire (GaN/Sa) and grown on silicon (GaN/Si) faced to implantation dopin&. Si+ was implanted on low doped n-type epilayers in order to create a plateau around 10(20)at.cm(-3). All the samples were capped with a silicon oxide and annealed between 1000 degrees C and 1150 degrees C. The surface quality was evaluated in terms of roughness, pit density and maximum pit diameter using Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Finally, the dopant electrical activation was studied with Ti-Al contacts using the circular Transfert Length Method (c-TLM). This study shows that low Specific Contact Resistance (SCR) values of 8x10(-5)Omega.cm(2) and 6x10(-6)Omega.cm(2) are respectively obtained on GaN/Sa sample annealed at 1150 degrees C-2min and on GaN/Si sample annealed at 1150 degrees C-30s, proving that good ohmic contacts are obtained on both materials. Nevertheless, a compromise has to be done between the low SCR values obtained and the GaN surface degradation, observed by AFM and SEM after the different annealing treatments and which could affect the good behaviour of the GaN devices.