Study Of Schottky Charactaristic Of High Performance AlGaN/GaN HEMT

Schottky contact is one of the most important processes in the fabrication of AlGaN/GaN HEMT. In order to increase the output power of HEMT, a good schottky contact with high schottky barrier, small ideal facter and low reverse leakage current is needed. So it is significative to study the schottky contact characteristic of AlGaN/GaN HEMT.In this paper, the effects of several related technology on schottky characteristic was investigated, and optimized results were obtained. Different surface treating method were compared. It was found that the density of surface states can be reduced effectively using O2 plasma etching the surface of AlGaN by ICP system and cleaning the surface with HF(40%): H2O(1:5) , and the ideal facter reduced from 2.6 to 1.8 compared with the sample without surface treating before schottky metals were deposited.The effects of ion implantation on the schottky contact characteristic was also studied,the result indicated that the implantation of B+ is the course of the degradation of the schottky contact. After optimizing of ion implantation process, the ideal factor decreased to 1.6, and when the reverse voltage was -20V, the leakage current was only 2.8×10-6A.The relationship between refractive index of SiN passivation film and the schottky characteristic was investingated lasterly, indicating that SiN film with refractive index of 2.3~2.4 given a better result, but further reseach was needed to settle the issue of large reverse leakage current after surface passivation.