Chapter 1 Ohmic Contacts to III-V Compound Semiconductors

Abstract

With the development of a wide variety of III-Vcompound semiconductor devices ( for e.g., injection lasers, light-emitting diodes, Gunn diodes, microwave Schottky-barrier and avalanche diodes, field-effect transistors, bistable resistors, and photodiodes), the need for low resistance, reproducible, stable, and reliable ohmic contacts to these semiconducting materials is increasingly felt. This chapter discusses the types of contacts. Among the various typed of contacts discussed in the chapter, the doped layer of low resistivity between metal system and semiconductor seems to be ideal for obtaining good ohmic contacts to compound semiconductors. From a considerable reduction in the contact resistance, the influence of injection by the ohmic contact is diminished because the lifetime and diffusion length of the minority carrier decrease appreciably with an increase in doping density. The fundamental processes at the surfaces and interfaces are rather limited and systematic about the metallurgical structure of various ohmic contacts to compound semiconductors. The availability of molecular beam epitaxial and ion implantation techniques may be possible to have more information about the ohmic contacts. Depending on the type of ohmic contact encountered in an actual device, a number of methods are available for the evaluation of specific contact resistance.