| GaN-based field effect transistors are of importance in the area of microwave, high-power, and high-temperature applications. The AlGaN/GaN system is well suited for these applications due to their high electron drift velocities, high breakdown fields, and relatively good thermal conductivities. The chemical stability and mechanical hardness of the nitrides also afford these devices the latitude of operating in harsh environments. The direct energy gap of III-nitrides and their alloys also make them ideal candidates for opto-electronic devices, especially for emitters and detectors working in the green to deep-UV region of the electromagnetic spectrum.; In this work, the development and characterization of electrical and materials performance of ohmic contacts are presented. Surface treatment techniques were developed to improve the electrical characteristics of ohmic contacts. Ti/Al/Mo/Au metallization scheme was developed to form ohmic contacts to n-GaN, n-AlxGa1-xN, and AlGaN/GaN HEMTs. Materials microstructural analysis techniques were used to understand the evolution of electrical behavior of these contacts at higher temperatures. |
