Characterization of gallium nitride materials for high-frequency and high-power devices

Abstract

In recent years, a significant progress has been made in the development of III-V Nitrides based devices. Materials such as Aluminium Nitride, Gallium Nitride, Indium Nitride and their alloys have been attractive due to the wide band-gap characteristic.

AlGaN/GaN based heterostructures are considered because of their capability of forming direct band-gap heterostructures, high breakdown voltage, high carrier velocity, and excellent chemical stability which are crucial for high power and high frequency applications as future wireless communication. However, the performance of AlGaN/GaN heterostructure High Electron Mobility Transistors (HEMTs) may depend on the ohmic contact characteristic at the interface of the heterostructure. Therefore, there is a necessity to develop a low contact resistance structure.

This report describes the electrical properties of GaN based material grown in Sapphire and Silicon substrate including AlGaN/GaN heterostructure and the development of an ohmic contact characteristic to the fabricated devices. The GaN based epitaxial layer had been grown by Molecular Beam Epitaxy system and its electrical characteristics were measured using Hall measurement system (Van Der Pauw Technique). Furthermore, the effect of AlN spacer layer insertion to the grown HEMT structure as well as its temperature dependent electrical characteristics had also been investigated.

A particular Ti/Al/Ni/Au contact structure had been successfully deposited in the AlGaN/GaN heterostructure by Electron Beam Evaporation. Its specific contact resistivity was extracted using Transfer Length Method. The resulted specific contact resistivity shows a considerably high value which can be improved through further study.