Improved contact performance of GaN film using Si diffusion

In this letter, we investigate a metalization process for reducing the cont act resistance on undoped GaN layers. The Si metal source was diffused succ essfully into the GaN films by using SiOx/Si/GaN/Al2O3 structures. By using a high-temperature annealing process, we diffused and activated the Si ato ms into the GaN film. This caused a heavy doped n-type GaN layer to be form ed near the GaN surface. Under high temperatures, such as a diffusion proce ss at 1000 degrees C, the as-deposited Ni/Al/Ti contact had good ohmic prop erties and a low specific contact resistivity (rho(c)) of 1.6 x 10(-3) Ohm cm(2). Rapid thermal annealing the contact at 800 degrees C for 30 s caused the rho(c) to decrease rapidly to 5.6 x 10(-7) Ohm cm(2). The Ni/Al/Ti con tact characteristics on the GaN films diffused at various temperatures are also discussed. (C) 2000 American Institute of Physics. [S0003-6951(00)0211 4-8].