Current Stability in Multi-Mesa-Channel AlGaN/GaN HEMTs

We develop and characterize multi-mesa-channel (MMC) AlGaN/GaN high-electron mobility transistors (HEMTs), in which a periodic trench structure is fabricated only under the gate electrode. A surrounding-field effect in the MMC structure results in a shallower threshold voltage and a smaller subthreshold slope than those of the standard planar-type HEMT. In addition, the MMC HEMT shows a low knee voltage and a weak dependence of on-resistance (R_ON) on the gate-drain distance. Following identical off-state bias stress, the MMC HEMT exhibits low current collapse. The relative decrease in access resistance of the MMC device compared with the planar device can reduce the effects of access resistance on the drain current. It is likely that a high impedance of each nanochannel also contributes to the current stability of the MMC HEMT.