Originally n-type Si-doped GaAs turns p-type after Li indiffusion and consequent annealing at 200–600°C. Temperature-dependent conductivity and Hall effect measurements carried out in the temperature range 30–300 K reveal conduction via impurity bands made up of shallow acceptors in addition to the valence-band conduction. Li diffusion into GaAs reduces the free-carrier concentration which leads to electrical resistivity as high as 107Ωcm. Annealing highly resistive samples at temperatures above 200°C significantly decreases the room-temperature resistivity to 0.1–1 Ωcm, depending on the annealing temperature. For samples annealed at 300–400°C we observe a metallic-type conduction which contributes to the conduction even at room temperature. In samples annealed at 500–600°C the temperature dependence of the resistivity indicates that impurity conduction sets in at temperatures below 100 K. We discuss this conduction change in relation to enhanced gallium vacancy (VGa) and gallium antisite (GaAs) concentration in Li indiffused and annealed samples.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 30 May 2003|