Design of E/D-mode InAlN/GaN HFET inverter and its robustness analysis

This article describes the design procedure towards a robust digital inverter that is intended to be fabricated on InAlN/GaN material heterostructure. Heterojunction field effect transistors (HFETs), regardless the material used, exhibit exceptional power delivery at high frequencies and also outstanding capability to withstand the operation in a very harsh environment. These properties make HFET transistors an excellent candidate for the future electronic applications. Effective utilization of such excellent properties requires monolithic integration of E-mode and D-mode transistors on a single die. However, the fabrication process of the heterostructures themselves and HFET transistors are not that mature and reliable as it is in the case of other materials used in microelectronics. In this paper, we describe the design of a basic logic circuit using both E-mode and D-mode HFETs as well as design of the output buffer. Due to immaturity of the technological process and physical constraints, the properties of depletion load based inverters and various output buffers are investigated in details with regard to the robustness.