Chapter 7 - Ion implant doping and isolation of GaN and related materials

Abstract

This chapter deals with ion implantation, which is the preferred method for selected-area doping of semiconductors because of its high spatial and dose control and its high throughput capability. In GaN, there are numbers of systematic reports detailing the achievement of n- and p-type doping and the application of ion implantation to improve ohmic contact resistance on heterostructure field-effect transistors and to produce p–n junctions for the fabrication of junction field-effect transistors and for light emitting diodes. Implantation is used for two different reasons in wide-band-gap nitrides. The first is to create doping by introducing additional dopants that are activated by high-temperature annealing to move the impurities onto substitutional lattice positions. The second is to create high-resistivity material by the introduction of deep-trap states that remove carriers from either band or decrease the sample conductivity. The usual environment for high-temperature annealing of III-nitrides is NH3, but this is inconvenient for processes such as rapid thermal annealing for implant activation and contact annealing for implant isolation.