Abstract: The influences of AlN passivation dielectric on the strain change of the AlGaN barrier layer and the high-temperature transport properties of AlGaN/GaN heterostructure have been investigated in the present work.The results show that the AlN passivation layer will induce an additional biaxial compressive strain to AlGaN barrier layer.Both the AlN and traditional Si₃N₄ passivation dielectrics can mitigate temperature-dependent strain relaxation of the AlGaN barrier,and AlN displayed a better effect.Compared to the traditional Si₃N₄ dielectric,the AlN film led to an obvious increase not only in the concentration but also in the mobility of the two dimensional electron gas（2DEG） in AlGaN/GaN heterostructure.Meanwhile,the variation of the 2DEG concentration with temperature in the AlN passivated sample is also smaller in comparison with that in the Si₃N₄ passivated sample.All these indicate that the AlN film is a promising passivation dielectric for AlGaN/GaN heterostructure devices.