V-Gate GaN HEMTs With Engineered Buffer for Normally Off Operation

We propose and demonstrate V-gate GaN high electron mobility transistors (HEMTs) with engineered buffers for normally off operation. By incorporating an AlGaN buffer under the GaN channel, net negative polarization charges are generated under the channel. These negative charges shift the threshold voltage of the GaN HEMT toward positive and therefore favor the realization of normally off operation. Using the engineered-buffer design coupled with our deep-recess V-gate structure, true normally off operation with reduced dc-RF dispersion was achieved.