Electrical insulation properties of carbon-controlled semi-insulating GaAs

Electrical insulation properties of liquid encapsulated Czochralski (LEC) GaAs crystals doped with carbon in concentrations ranging from 5×10 15 cm -3 to 2.0×10 16 cm -3 were investigated. The leakage current decreased with increase of carbon concentration and the turn-on voltage at which current starts to increase abruptly became as high as 75 V, corresponding to the average electric field of 150 kV/cm. At low voltage, the leakage current was determined by the resistivity which depended on the carbon concentration. The turn-on voltage was not temperature-dependent in the case of high carbon concentration and can be explained by the theory of trap-filled voltage up to 50 V. This improvement of the insulation can be achieved not only by carbon doping but also by proper ingot annealing by which native defects other than EL2 are diminished and the microscopic distribution of the electrical properties is made uniform.