ABSTRACT
Group III-V nitride compound semiconductors such as Gallium Nitride(GaN) and Aluminum Gallium Nitride(AlGaN) exhibit distinctive combination of properties like high break down field, large energy band gap, good thermal conductivity, high mobility and high saturation velocity. Due to these properties, GaN based devices outperform existing Si and SiC based devices for power electronic applications. There has been a rapid progress in the design and development of GaN based devices and circuits since the demonstration of first GaNbased transistor. Since early 1990s, GaN has been considered as avery interesting and highly promising material for both optical and high power microwave applications. Owing to the high defect density present in native GaN material, early studies of GaN and related compounds showed uncertainty on whether devices based on this material could ever be used for practical applications. Nevertheless, with better understanding of effect of these defects on device performance along with improvement in the epitaxial growth technology, GaN based technology has been successfully in use for high power applications. Trapping related reliability issues still remain a majorobstacle for AlGaN/GaN High Electron mobility Transistors (HEMT), thus preventing themfrom being adoptedwidely for high-voltage and high-temperature applications. It is essential to analyze and study trapping effects in AlGaN/GaN HEMTs because of two important reasons. First, theylimit DC and RF performance of the device. Secondly they also play an important role in reliability of the device in high power applications. Thedevice performance severely degrades when it operates at high voltage as the electrons get trapped in various locations in the device. It has also been seen that the trapping effects rise after device degradation. Performance and thus reliability of the device thus greatly reduces by increased trapping.
