ABSTRACT
A HEMT or a Hetero-junction FET is a key device for high speed digital circuits and low noise microwave circuits. The applications include computing, telecommunications, and instrumentation on a broad perspective. The device also shows high performance in RF design. The major advances and utilization of wide band gap semiconductor devices along with group-III nitrides have led to the development of AlGaN/GaN HEMTs. Better noise performance is one of the leading parameters that make HEMTs to stand out from all the other kinds of Field Effect Transistors.
DG-HEMTs (Double Gate HEMT), in their extrinsic form, exhibit an evidently superior frequency performance and a higher immunity to short-channel effects due to the reduced parasitic resistances and lower drain conductance. It is the emergent solution which provides enhancements over SG-HEMT (Single Gate HEMT) by virtue of its double gate and also for same DC, due to double hetero-junctions, which virtually increases the value of aspect ratio for very small gate lengths. Short-channel effects are less prominent in DG-HEMTs, leading to a better intrinsic dynamic performance. The structure of a HEMT device is formed by joining two or more different band gap materials and the most important DG HEMTs are AlGaN/GaN HEMT and InGaAs/InAs.
The chapter begins with High Electron Mobility Transistors, its importance and classifications. Section 16.1 explains about AlGaN/GaN DG-HEMT followed by materials used for fabrication, device fabrication and device operation. The DC and RF characteristics are explained in section 16.2. Section 16.3 gives an overview about InGaAs/InAs DG-HEMT followed by its DC and RF characteristics in section 16.4. The final section of the chapter gives an idea about the parasitics observed in DG-HEMT.
