Ge-ion implantation and activation in (100) -Ga₂O₃ for ohmic contact improvement using pulsed rapid thermal annealing

In this work, we analyze the optimum annealing conditions for the activation of Ge-implanted beta-Ga2O3 in order to reach low ohmic contact resistances. The experiments involved the use of a pulsed rapid thermal annealing treatment at temperatures between 900 and 1200 degrees C in nitrogen atmosphere. Our investigations show remarkable changes in the surface morphology involving increased surface roughness after high-temperature annealing above 1000 degrees C as well as a significant redistribution of the implanted Ge. Nevertheless, the specific contact resistance is strongly reduced by one order of magnitude after annealing at 1100 degrees C, reaching a record value of 4.8 x 10(-7) Omega cm(2) at an implantation activation efficiency of 14.2%. The highest activation efficiency of 19.2% and lowest sheet resistances were reached upon annealing at 1200 degrees C, which, in turn, showed inferior ohmic contact properties due to a severe increase of the surface roughness. Our results verify the high potential of applying high-temperature annealing processes above 1000 degrees C after Ge implantation for reaching low ohmic contact resistances to beta-Ga2O3.