We have carried out DC and transient measurements in order to investigate the kink effect in AlGaN/GaN HEMTs. A correlation between kink and threshold voltage shift has been found. Kink is possible due to negative charge build-up, taking place at low VDS values followed by negative charge detrapping or compensation, occurring for high VDS values. Dynamic measurements strongly suggests carrier trapping and detrapping as possible explanation. Photo-stimulated measurements have been also carried out in order to verify whether charge build-up and removal were due to trapping/detrapping mechanisms
