Abstract: In order to improve the surface electric field and temperature distribution of conventional AlGaN/GaN HEMT devices and enhance the breakdown voltage and stability of the devices, a new AlGaN/GaN HEMT device structure with uniform groove potential barrier (UGB) is proposed.The UGB-AlGaN/GaN HEMT structure reduces the polarization intensity of the AlGaN layer by introducing a uniformly distributed notch AlGaN barrier between the gate electrode and the drain electrode, resulting in a decrease in the channel 2DEG concentration and the formation of a low concentration 2DEG region, which changes the channel 2DEG distribution of the device from a uniform distribution to a notch step-like distribution, thereby regulate the surface electric field of the device. The electric field modulation effect is used to form a new electric field peak on the right side of the notch to effectively reduce the peak electric field at the gate edge. At the same time, the device channel surface temperature distribution is optimized to make the UGB-AlGaN/GaN HEMT surface temperature distribution more uniform simulation results of Silvaco TCAD show that the uniform notch AlGaN barrier can regulate the surface electric field distribution of the HEMT device under the high voltage of the off-state drain, thus ensuring the surface electric field distribution of the UGB-AlGaN/GaN HEMT device with the distance between the gate electrode and the drain electrode of 10 μm. AlGaN/GaN HEMT devices with a 10 μm distance between the gate electrode and the drain electrode can achieve a breakdown voltage of 821 V, which is 3.1 times higher than the breakdown voltage (260 V) of conventional devices. At the same time, the characteristic on-resistance of UGB-AlGaN/GaN HEMT devices is only 0.87 mΩ ·cm², thus achieving a quality factor of up to 772 MW ·cm^-2. The HEMT devices based on the new uniform notch barrier structure have a high breakdown voltage while maintaining a low characteristic on-resistance and good temperature characteristics, which makes the structure promising for high power electronic components.