UBC Theses and Dissertations

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UBC Theses and Dissertations

Ion implanted GaAs Mesfet technology Lowe, Kerry Steven


The availability of high quality semi-insulating GaAs substrates is essential to the development of GaAs metal semiconductor field effect transistor (MESFET) integrated circuits. Problems have been encountered with horizontal Bridgman grown substrates since, for example, these must be doped with Cr to make then semi-insulating and the Cr tends to diffuse during device processing. Undoped semi-insulating GaAs substrates can be grown by the Liquid Encapsulated Czochralski (LEC) technique and allow the possibility of forming active regions by the process of implanting dopants directly into the substrate. The purpose of this thesis was to develop at the University of British Columbia a GaAs MESFET technology based on direct ion implantation and to develop methods to assess undoped LEC substrates for Cominco Limited, Trail, B.C. A test device array consisting of structures for process, material, and device characterization was designed and then fabricated on Cominco wafers by a direct implantation process. Measurements on the test device array elements showed that this initial process could be used to produce MESFET's operational up to 3 GHz and that the test device array will be useful for monitoring future process developments and improvements. In addition, a channel conductance deep level transient spectroscopy system, a photocurrent deep level transient spectroscopy system, and a novel MESFET drain current hysteresis analysis system were developed to examine deep levels in GaAs and deep level trapping effects in GaAs MESFET's.

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