Interfacial and electrical characteristics of tetragonal HfO2/Al2O3 multilayer grown on AlGaN/GaN
We report the study of HfO2/Al2O3 multilayer (HAOM) that is deposited on AlGaN/GaN heterostructure by plasma enhanced atomic layer deposition (PEALD). The properties and passivation effect of HAOM, sole Al2O3 and HfO2 films were investigated. After high-temperature rapid thermal annealing (RTA) of 850 °C, the formation of tetragonal phase in HAOM is presented. Al incorporates into HfO2 layers during RTA, which facilitates the formation of tetragonal HfO2. The HAOM film reveals an effective dielectric constant of ~ 30.2, a critical electric field of 7.6 MV/cm and leakage of only 6.8 × 10−4 mA/cm2 at gate bias of |Vg − Vfb| = 10 V. The HAOM insulating layer is shown to be effective in suppressing leakage current. In particular, the HAOM MIS diode current is reduced by both 6 orders of magnitude at negative bias of − 10 V and forward bias of 1.5 V compared with a conventional Schottky diode.
This work was sponsored by Shanghai Sailing Program (Grant No. 17YF1413900). The authors thank the staff of beam line BL14B1, Shanghai Synchrotron Radiation Facility, for the GIXRD measurements.