Hybrid Gate p-GaN Power HEMTs Technology for Enhanced V_th Stability

A novel hybrid gate p-GaN power high-electron-mobility transistor (Hyb-HEMT) technology is proposed in this work to effectively enhance threshold voltage $(V_{th})$ stability without obvious gate leakage current $(I_{gss})$ degradation. In this device concept, gate structure consists of spaced ohmic-type p-GaN metal dots and Schottky-type p-GaN metal. Charge storage effect can be alleviated through a free-carrier “discharge path” induced by ohmic-type p-GaN region, thus enhancing the V th stability. Surrounding geometry distribution of Schottky-type p-GaN metal can take full advantage of depletion region, ensuring a relatively low I gss . It is experimentally demonstrated that activation energy $(E_{A})$ of proposed Hyb-HEMT is only 0.59eV, and such a device can suppress V th shift within only 0.1V (0.42V for commercial HEMT) under DC drain/gate bias stress and repetitive unclamped-inductive-switching (UIS) stress.