A novel In0.3Ga0.7As0.99N0.01(Sb)/GaAs high-electron-mobility transistor has been successfully investigated for the first time by incorporating surfactant Sb atoms during the InGaAsN channel growth by molecular beam epitaxy (MBE). Superior stable thermal characteristics, including a thermal threshold coefficient (∂Vth/∂T) of -0.807 mV/K and a high-temperature linearity (∂GVS/∂T) of -0.053 mV/K, were achieved because of the improved crystalline quality and the enhanced carrier confinement capability of the In0.3Ga0.7As0.99N0.01(Sb)/GaAs heterostructure. The device also demonstrated a peak extrinsic transconductance (gm,max) of 94 (109) mS/mm at 450 (300) K.