Electrical Properties of Zinc and Cadmium Ion Implanted Layers in Gallium Arsenide

Ion implantation has been used to dope high resistivity, single crystal gallium arsenide with cadmium and zinc. Implants were made with 20 kv ions into heated substrates held at 400°C. Electrical characteristics of the implanted layers have been studied as a function of isothermal and isochronal annealing cycles. The surface resistivity, average mobility, and carrier concentration in the layer have been determined by Hall measurements; it has been observed that these electrical properties are dependent on post‐implantation annealing and generally tend to improve significantly with annealing at relatively low temperatures for short times. For example, annealing of cadmium implanted samples at temperatures up to 800°C for less than 1 hr was sufficient to increase mobility from a value of 4 cm2/v sec to approximately 180 cm2/v sec, and to reduce sheet resistivity from approximately . Additional annealing for 20 min at 900°C further reduced sheet resistivity to 300 ohm/cm and increased surface carrier concentration to a maximum of . The increased carrier concentration eventually resulted in decreased mobility because of impurity scattering.

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