The　forward　Schottky　characteristic　method,　utilizing　the　temperature　dependence　of　forward　gate-source　Schottky　junction　voltage,　has　been　used　to　measure　the　transient　temperature　rise　under　DC　and　cycle　pulse　for　multi-finger　AlGaN/GaN　high　electron　mobility　transistor.　The　effect　of　electrical　pulse　on　channel　temperature　has　been　studied.　The　transient　temperature　rise　of　channel　under　pulses　with　different　duty　cycles　and　frequencies　are　determined,　respectively.　The　measurement　results　show　that　operation　under　high　frequency　and/or　low　duty　cycle　can　improve　the　lifetime　and　performance　reliability　of　AlGaN/GaN　HEMT　devices　effectively.　Furthermore,　the　measurement　results　are　found　to　be　consistent　with　the　electro-thermal　simulation　results　performed　for　the　device.　(C)　2013　AIP　Publishing　LLC.