Abstract: Although outstanding microwave power performance of AlGaN/GaN HEMTs has been reported,drain current collapse is still a problem.In this paper,an experiment was carried out to demonstrate one factor causing the collapse.Two AlGaN/GaN samples were annealed under N2-atmosphere with and without carbon incorporation,and the XPS measurement technique was used to determine that the concentration of carbon impurity in the latter sample was far higher than in the former.From the comparison of two Id-Vds characteristics,we conclude that carbon impurity incorporation is responsible for the severe current collapse.The carbon impurity-induced deep traps under negative gate bias stress can capture the channel carriers,which release slowly from these traps under positive bias stress,thus causing the current collapse.

Key words: AlGaN/GaN HEMT, current collapse, carbon impurity, deep trap