Sidewall Dominated Characteristics on Fin-Gate AlGaN/GaN MOS-Channel-HEMTs

The fin-gate structure was fabricated onto AlGaN/GaN MOS channel-high electron mobility transistors (MOSC-HEMTs), and the fin sidewall contribution to the MOS channel characteristics was investigated. In fin-gate MOSC-HEMTs (Fin-MOSC-HEMTs) with 120-nm fin width, significant suppression of short channel effect is obtained, but the threshold voltage (V_th) becomes lower than that of conventional MOSC-HEMTs. The fin width dependence shows continuous V_th decrease by decreasing the fin width, indicating that the narrower fin-gate channel is dominated by the fin sidewalls that are depletion mode nature. The channel sheet resistance extracted from channel length dependence and device transconductance for Fin-MOSC-HEMTs are superior to those of conventional MOSC-HEMTs when they are normalized by effective gate width as the summation of fin width, indicating contribution from sidewalls to channel conduction. Temperature dependence of V_th shows clearly different behavior between the MOSC-HEMT and Fin-MOSC-HEMT. These results demonstrate sidewall-dominated characteristics of these Fin-MOSC-HEMTs.