Effect of As Interstitial Diffusionon on the Properties of Undoped Semi-insulating LECGaAs

Annealing was carried out at 950 and 1120 ℃ under various As pressure for undoped (ND) semi-insulating (SI) LECGaAs. The effects of annealing on native defects and electrical properties were investigated. Experimental results indicate that, after an annealing at 950 ℃ for 14 h under low As pressure, the Hall mobility decreases and the resistivity increases dramatically for the samples. These changes in electrical properties are due to the generation of intrinsic acceptor defects, and the generation of the intrinsic acceptor defects originates from the outdiffusion of As interstitial at high temperature. The generation of the intrinsic defects and these changes in electrical properties can be suppressed by increasing the applied As pressure during annealing. The concentration of the main donor defect El2 (AsGaVGa ) can be decreased by about one order of magnitude by an evacuated annealing at 1120 ℃ for 2? h followed by a fast cooling. The decrease in El2 concentration can also be suppressed by increasing the As pressure during annealing.