Drain Current Stability and Controllability of Threshold Voltage and Subthreshold Current in a Multi-Mesa-Channel AlGaN/GaN High Electron Mobility Transistor

The surrounding-field effect in a multi-mesa-channel (MMC) with an AlGaN/GaN structure, in which a periodic trench structure is fabricated directly under a gate electrode, was successfully observed. This effect resulted in a shallower threshold voltage, a smaller subthreshold slope, and a higher current drivability of a high electron mobility transistor (HEMT) than those of a standard planar-type HEMT. In addition, the MMC HEMT showed a low knee voltage, even with a wide spacing between the gate and drain electrodes. Excellent current, stability in the saturation region of the MMC HEMT, probably due to the effective radiation of heat from both mesa sides of the channel, was also observed. Both planar and MMC HEMTs showed similar breakdown voltages under off-state operation, indicating no significant degradation in the breakdown characteristics of AlGaN/GaN HEMTs with a periodic trench structure in the gate region. (C) 2009 The Japan Society of Applied Physics