TABLE OF CONTENTS This chapter will cover most of the basic GaAs-related processing steps for GaAs field effect transistors, including most of the front-end steps. Active steps are those that relate to the fabrication of the GaAs field effect transistor and do not include the interconnections or the integration of passive elements. FET fabrication and operation require an understanding of the GaAs semiconductor surface and its interface to metal junctions for etching, doping, contact formation and some particular aspects of performance optimisation. This chapter will draw heavily on material presented in the preceding chapters.
The basics of field effect transistors and their different types are given in Section 8.2 [1 3]. That section starts with a tutorial and continues to relate FET operation to the processing methods, device geometries and materials. It also highlights the main reliability issues and relates them to FET structures, processing and materials. Sections 8.3, 8.4 and 8.5 present the details of the main active processing methods: ion implantation, ohmic and Schottky metal formation, recessed gate etching and passivation.
The field effect transistor was proposed long before it was demonstrated in 1952. In the 1920s, semiconductors were poorly understood because of poorly developed materials technology. Two of the greatest materials problems of that time were a lack of purity and a lack of understanding of the semiconductor surface and its oxides. Both of these areas saw great progress in the 1950s with the development of zone refining methods of purification, among other...
