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UBC Theses and Dissertations

Gallium arsenide materials and device fabrications Tan, Kim Wah


The purpose of this work was to study certain aspects of device fabrication and material properties of ion implanted MESFETs in semi-insulating LEC GaAs. The fabrication technology and materials properties of GaAs are presently the chief limitations in the way of application of GaAs ion-implanted devices in high speed circuits. One part of the work involved studies on the effects of etching away the surface layers of the starting semi-insulating LEC GaAs. The point here is that it appears that impurities and other defects can sometimes be concentrated at the surface. A test structure containing MESFETs, Schottky diodes and van der Pauw crosses was fabricated using ion implantation on etched and unetched substrates. Improved activation and device characteristics were found on the etched sample. The second part of the work involved studies of the effects of dislocations on device characteristics. The topic is important because dislocations may give scatter in the threshold voltage of MESFETs which would, naturally, become a problem for large scale integration. Arrays of devices were fabricated and their characteristics measured. The position of dislocations was located by etching in such a way as to leave the ghost of the devices behind. The results were unfortunately not conclusive because of the difficulty in accurately etching the samples. We were subsequently forced to use fewer samples than planned.

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