Hopping conduction in lithium diffused and annealed GaAs

Temperature dependent conductivity and Hall effect measurements were carried out in the temperature range 30-300 K on Li-diffused and annealed GaAs. Li in-diffusion into GaAs reduces the free carrier concentration which leads to electrical conductivity as low as 10/sup -7/ S/cm. Annealing the lithium diffused samples at temperatures above 200/spl deg/C significantly increases the room temperature conductivity to 1-10 S/cm, depending on the annealing temperature. In samples annealed at 300-500/spl deg/C the temperature dependence of the conductivity indicates that hopping conduction sets in at temperatures below 100 K. We relate this to enhanced gallium vacancy (V/sub Ga/) and gallium antisite (Ga/sub As/) concentration in Li in-diffused and annealed samples.