Ohmic　contacts　with　Ti/Al/Ti/Au　source　and　drain　electrodes　on　AlGaN/GaN　high　electron　mobility　transistors　(HEMTs)　were　fabricated　and　subjected　to　rapid　thermal　annealing　(RTA)　in　flowing　N2.　The　wafer　was　divided　into　5　parts　and　three　of　them　were　annealed　for　30　s　at　700,　750,　and　800°C,　respectively,　the　others　were　annealed　at　750°C　for　25　and　40　s.　Due　to　the　RTA,　a　change　from　Schottky　contact　to　Ohmic　contact　has　been　obtained　between　the　electrode　layer　and　the　AlGaN/GaN　heterojunction　layer.　We　have　achieved　a　low　specific　contact　resistance　of　7.41　×　10-6　Ω·cm2　and　contact　resistance　of　0.54　Ω·mm　measured　by　transmission　line　mode　(TLM),　and　good　surface　morphology　and　edge　acuity　are　also　desirable　by　annealing　at　750°C　for　30　s.　The　experiments　also　indicate　that　the　performance　of　ohmic　contact　is　first　improved,　then　it　reaches　a　peak,　finally　degrading　with　annealing　temperature　or　annealing　time　rising.　©　2014　Chinese　Institute　of　Electronics.