Study On In-Situ Growth Of Dielectric MIS-HEMT

GaN-based high-electron mobility transistors (HEMTs) have demonstrated outstanding performance for high-power and high-frequency applications. However, they also have some defects, such as the larger gate leakage current and current collapse, which would seriously limit their applications. Recently, MIS-HEMTs have been taken in for their comparatively better control of gate leakage and current collapse. However, the high concentration of interface state traps has always been the key limitations of MIS-HEMT devices. In this thesis, AlN will be grown in-situ as the dielectric material of MIS-HEMTs, in order to condense the process and get a lower density of interface state traps. This brings desired results.The MIS-HEMTs with low temperature (LT-AlN MIS-HEMT) and high temperature (HT-AlN MIS-HEMT) AlN materials as dielectric layer are manufactured. The measurements at room temperature indicate that the LT-AlN MIS-HEMT can effectively reduce the gate leakage current by two orders and increase the breakdown voltage greatly. Meanwhile, the HT-AlN MIS-HEMT can effectively suppress current collapse. Long term on-state and off-state stress are forced on the HT-AlN MIS-HEMT. After on-state stress, due to the reduction of the concentration of 2DEG, the increased resistance in channel induces the degradation of the device. After off-state stress, due to the high electric field during off-state stress, lots of traps are generated in the surface or buffer layer, which enhance the kink effect and gate-lag effect.In order to further improve the performance of the HT-AlN MIS-HEMT, the high-temperature AlN is oxidized. It is found that oxidation can effectively reduce gate leakage current by two orders, and significantly suppresses the current collapse effect.