Improving the off-state characteristics and dynamic on-resistance of AlInN/AlN/GaN HEMTs with a GaN cap layer

The electrical characteristics of a series of AlInN high-electron-mobility transistors (HEMTs) with a GaN cap layer ranging from 0 to 26 nm are investigated for power switching applications. The breakdown voltage (V_B), mobility of two-dimensional electron gas, on-state resistance (R_on), and dynamic R_on of the HEMTs are improved by increasing the cap layer thickness. The improved electrical characteristics are attributed to the GaN cap layer, which not only reduces the surface E-field but also raises the conduction band of the barrier layer and effectively prevents electrons from being trapped in the AlInN barrier and above.