| dc.description.abstract | This paper focuses on the study of the Au-free recessed ohmic contact GaN, and then applies it to the GaN HEMTs for electrical discussion and research. The research includes epitaxy structures material, device fabrication, electrical analysis, and Silvaco TCAD simulation.
For AlGaN/GaN epitaxial structures, this study reviews the ohmic contact, electrical characteristics analysis results of Au-based AlGaN/GaN HEMT. The best ohmic contact resistance (RC = 0.89 Ω∙mm) can be obtained under the conditions of the recess depth and the recess pattern are 5.5 nm and 1/3/5 μm, and make Au-based recessed ohmic contact AlGaN/GaN HEMT under this condition and compare with Au-based non-recessed ohmic contact AlGaN/GaN HEMT. The results show that the recess pattern design reduces the ohmic contact resistance to improve the electrical characteristics, but there is a serious current collapse in the dynamic characteristics. Therefore, this study uses Au-free ohmic metal with 550 ℃ low annealing temperature to explore the analysis of ohmic contact and electrical characteristics. According to the results, the best ohmic contact resistance (RC = 0.98 Ω∙mm) can be obtained when the recess depth and the recess pattern are 27.5 nm and 1/3/5 μm, and the Au-free recessed ohmic contact AlGaN/GaN HEMT is fabricated under this condition. The results show that compared to the Au-based recessed ohmic contact HEMTs, the problems of device breakdown voltage characteristics and current collapse are improved. The research has shown that Au-free ohmic metal with low annealing temperature not only solves the problem of CMOS technology incompatibility but also improves the problem of device characteristics.
In addition, for AlInGaN/GaN epitaxial structure with low sheet resistance, a recess pattern of 1/3/5 μm can also obtain the best ohmic contact resistance (RC = 1.14 Ω∙mm), and the Au-free recessed ohmic contact AlInGaN/GaN HEMT is fabricated under this condition for electrical analysis. | en_US |