Comparative study on nitridation and oxidation plasma interface treatment for AlGaN/GaN MIS-HEMTs with AlN gate dielectric

This paper demonstrated the comparative study on interface engineering of AlN/AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) by using plasma interface pre-treatment in various ambient gases. The 15 nm AlN gate dielectric grown by plasma-enhanced atomic layer deposition significantly suppressed the gate leakage current by about two orders of magnitude and increased the peak field-effect mobility by more than 50%. NH3/N-2 nitridation plasma treatment (NPT) was used to remove the 3 nm poor-quality interfacial oxide layer and N2O/N-2 oxidation plasma treatment (OPT) to improve the quality of interfacial layer, both resulting in improved dielectric/barrier interface quality, positive threshold voltage (V-th) shift larger than 0.9 V, and negligible dispersion. In comparison, however, NPT led to further decrease in interface charges by 3.38 x 10(12) cm(-2) and an extra positive Vth shift of 1.3 V. Analysis with fat field-effect transistors showed that NPT resulted in better sub-threshold characteristics and transconductance linearity for MIS-HEMTs compared with OPT. The comparative study suggested that direct removing the poor interfacial oxide layer by nitridation plasma was superior to improving the quality of interfacial layer by oxidation plasma for the interface engineering of GaN-based MIS-HEMTs.