AlGaN/GaN high electron mobility transistors(HEMTs) grown on Fe-modulation-doped(AID) and unintentionally doped(UID) GaN buffer layers are investigated and compared.Highly resistive GaN buffers(10~9 Ω·cm) are induced by individual mechanisms for the electron traps’ formation:the Fe AID buffer(sample A) and the UID buffer with high density of edge-type dislocations(7.24 × 10~9 cm~(-2),sample B).The 300 K Hall test indicates that the mobility of sample A with Fe doping(2503 cm~2 V~(-1) s~(-1)) is much higher than sample B(1926cm~2V~(-1)s~(-1))due to the decreased scattering effect on the two-dimensional electron gas.HEMT devices are fabricated on the two samples and pulsed Ⅰ-Ⅴ measurements are conducted.Device A shows better gate pinch-off characteristics and a higher threshold voltage(-2.63 V) compared with device B(-3.71 V).Lower gate leakage current Igs of device A(3.32 × 10~(-7) A) is present compared with that of device B(8.29 × 10~(-7) A).When the off-state quiescent points Q_2(V_(GQ2) =-8 V,V_(DQ2) = 0 V) are on,V_(th) hardly shifts for device A while device B shows +0.21 V positive threshold voltage shift,resulting from the existence of electron traps associated with the dislocations in the UID-GaN buffer layer under the gate.Under pulsed Ⅰ-Ⅴ and transconductance G_m-V_(GS) measurement,the device with the Fe MD-dopcd buffer shows more potential in improving reliability upon off-state stress. Highly resistive GaN buffers (10-9 Ω · cm) are induced by individual (GaN) layers. GaN-based high electron mobility transistors (HEMTs) are grown on Fe-modulated-doped (AID) and unintentionally doped GaN buffer layers mechanisms for the electron traps’ formation: the Fe AID buffer (sample A) and the UID buffer with high density of edge-type dislocations (7.24 × 10 ~ 9 cm -2, sample B). The 300 K Hall test indicates that the mobility of sample A with Fe doping (2503 cm -2 V -1 s -1) is much higher than sample B (1926 cm -2V -1 s -1) due to the decreased scattering effect on the two-dimensional electron gas. HEMT devices are fabricated on the two samples and pulsed I-V measurements are conducted. Device A shows better gate pinch-off characteristics and a higher threshold voltage (-2.63 V) compared with device B (-3.71 V) .Lower gate leakage current Igs of device A (3.32 × 10 -7 A) is present compared with that of device B (8.29 × 10 -7) A) .When the off-state quiescent p oints Q_2 (V_ (GQ2) = -8 V, V_ (DQ2) = 0 V) ​​are on, V_ (th) hardly shifts for device A while device B shows +0.21 V positive threshold voltage shift, resulting from the existence of electron traps associated with the dislocations in the UID-GaN buffer layer under the gate. Unders pulsed I-V and transconductance G_m-V_ (GS) measurement, the device with the Fe MD-dopcd buffer shows more potential in improving reliability on off-state stress.