This book focusses on III-V high electron mobility transistors (HEMTs) including basic physics, material used, fabrications details, modeling, simulation, and other important aspects. It initiates by describing principle of operation, material systems and material technologies followed by description of the structure, I-V characteristics, modeling of DC and RF parameters of AlGaN/GaN HEMTs. The book also provides information about source/drain engineering, gate engineering and channel engineering techniques used to improve the DC-RF and breakdown performance of HEMTs. Finally, the book also highlights the importance of metal oxide semiconductor high electron mobility transistors (MOS-HEMT). Key Features Combines III-As/P/N HEMTs with reliability and current status in single volume Includes AC/DC modelling and (sub)millimeter wave devices with reliability analysis Covers all theoretical and experimental aspects of HEMTs Discusses AlGaN/GaN transistors Presents DC, RF and breakdown characteristics of HEMTs on various material systems using graphs and plots

This thesis deals with the analysis and optimization of some of the most prominent non-ideal effects in AlGaN/GaN high electron mobility transistors used in microwave applications as well as the optimization of the RF gain. The effect of current collapse, the root cause of leakage currents as well as field-dependent self-heating effects have been investigated by eletrical characterization using well established techniques and have been analyzed using 2-dimensional physical device simulations. It will be shown that the origin of all effects is strongly related to the device surface and some are even competing effects making device optimization a challenge. However, a detailed localization of the regions affecting device performance will be given leading to a better understanding for fabrication process optimization. Finally, I simulation study is conducted giving suggestions for RF gain improvement based on very simple device layout variations.

Gallium Nitride (GaN) based high electron mobility transistors (HEMTs) outperform Gallium Arsenide (GaAs) and silicon based transistors for radio frequency (RF) applications in terms of output power and efficiency due to its large bandgap (~3.4 eV@300 K) and high carrier mobility property (1500 - 2300 cm^2/(V-s)). These advantages have made GaN technology a promising candidate for future high-power microwave and potential millimeter-wave applications. Current GaN HEMT models used by the industry, such as Angelov Model, EEHEMT Model and DynaFET (Dynamic FET) model, are empirical or semi-empirical. Lacking the physical description of the device operations, these empirical models are not directly scalable. Circuit design that uses the models requires multiple iterations between the device and circuit levels, becoming a lengthy and expensive process. Conversely existing physics based models, such as surface potential model, are computationally intensive and thus impractical for full scale circuit simulation and optimization. To enable efficient GaN-based RF circuit design, computationally efficient physics based compact models are required. In this thesis, a physics based Virtual Source (VS) compact model is developed for GaN HEMTs targeting RF applications. While the intrinsic current and charge model are developed based on the Virtual Source model originally proposed by MIT researchers, the gate current model and parasitic element network are proposed based on our applications with a new efficient parameter extraction flow. Both direct current (DC) of drain and gate currents and RF measurements are conducted for model parameter extractions. The new flow first extracts device parasitic resistive values based on the DC measurement of gate current. Then parameters related with the intrinsic region are determined based on the transport characteristics in the subthreshold and above threshold regimes. Finally, the parasitic resistance, capacitance and inductance values are optimized based on the S-parameter measurement. This new extraction flow provides reliable and accurate extraction for parasitic element values while achieving reasonable resolutions holistically with both DC and RF characteristics. The model is validated against measurement data in terms of drain current, gate current and scattering parameter (S-parameter). This model provides simple yet clear physical description for GaN HEMTs with only a short list of model parameters compared with other empirical or physics based models. It can be easily integrated in circuit simulators for RF circuit design.

The topic of this monograph is the physical modeling of heterostructure devices. A detailed discussion of physical models and parameters for compound semiconductors is presented including the relevant aspects of modern submicron heterostructure devices. More than 25 simulation examples for different types of Si(Ge)-based, GaAs-based, InP-based, and GaN-based heterostructure bipolar transistors (HBTs) and high electron mobility transistors (HEMTs) are given in comparison with experimental data from state-of-the-art devices.