Trapping　effects　in　GaN　HEMTs　still　limit　their　performance.　The　current-transient　methodology　has　shown　advantages　in　characterizing　traps　in　the　device.　However,　the　voltage　drift　may　cause　errors　in　measurements　with　high　accuracy　requirements.　In　this　paper,　we　present　a　methodology　to　characterize　traps　in　GaN　HEMTs　using　the　voltage-transient　measurements.　We　demonstrate　the　advantages　of　this　method　in　terms　of　simplicity　and　effectiveness.　In　particular,　it　avoids　the　said　problem　due　to　the　optimized　measuring　circuit.　With　this　method,　we　have　identified　the　time　constants　and　energy　levels　of　traps　in　the　AlGaN　barrier　layer　and　the　GaN　buffer　layer,　respectively,　in　the　devices.　Their　trapping　and　de-trapping　mechanisms　were　also　demonstrated　at　various　temperature　measurements.　A　classic　exponential　dependence　of　the　degradation　rate　on　the　channel　current　was　identified.　©　2018　Elsevier　Ltd