We demonstrate a novel design of large-size device in AlGaN/GaN high-electron-mobility transistor (HEMT). Depletion mode (D-mode) HEMTs and enhancement mode (E-mode) HEMTs are fabricated in our research. The saturation current of D-mode HEMTs is over 6A. By using Cascode structure, the D-mode HEMT becomes a normally-off device efficiently, and the threshold voltage of it rises from-7V to 2V. By using BCB (Benzocyclobutene) as the passivation, the E-mode HEMT shows an excellent characteristic. Also, when the VGS of the E-mode HEMT is over 9V, it still shows a good performance.