The　temperature　dependence　of　the　Schottky　voltage　under　a　forward　constant　current　was　used　as　a　means　to　measure　the　transient　temperature　characteristics　of　gallium　nitride　(GaN)　high-electron-mobility　transistors　(HEMTs).　However,　the　degradationof　the　Schottky　diode　leads　to　error　in　the　calculated　temperature　measurement　results,　especially　at　a　high　forward　Schottky　current.　In　this　paper,　we　characterized　the　degradation　of　GaN　HEMT　Schottky　diodes　under　forward　bias　using　pulsed　current-voltage　measurements.　The　forward　Schottky　voltage　behavior　at　constant　currents　of　0.2,　0.35,　0.5,　1,　1.5,　and　2　mA　was　monitored.　In　particular,　the　vertical　temperature　distribution　was　corrected　experimentally　based　on　the　transient　voltage　measurements.　The　success　of　this　correction　indicates　that　the　said　artifacts　can　be　removed　using　the　transient　voltagemeasurements.　This　method　increases　the　accuracy　of　temperature　measurements　when　the　temperature　dependence　of　the　Schottky　voltage　is　used　to　characterize　the　behavior　of　GaN　HEMTs.