Off‐state drain current and breakdown voltage of AlGaN/GaN MIS‐HEMT with multilayered gate insulator

We report the fabrication of AlGaN/GaN high electron mobility transistors (HEMT) with high‐k /SiN and high‐k /SiO2/SiN gate structures. HfO2, ZrO2, TiO2 and Ta2O5 were used as high‐k materials. Both high‐k /SiN and high‐k /SiO2/SiN metal‐insulator‐semiconductor (MIS) HEMTs showed good operating characteristics. However, in the case of high‐k /SiN MIS‐HEMT, the off‐state drain current was large. On the other hand, in the case of the high‐k /SiO2/SiN MIS‐HEMT, the off state current was significantly reduced due to the presence of the SiO2 layer, and the breakdown voltage characteristics were improved. The breakdown voltages of HfO2/SiO2/SiN MIS‐HEMT and ZrO2/SiO2/SiN at gate‐drain distance Lgd = 28 μm were 1.8 kV and 1.7 kV, respectively. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)