Electrical properties of Te-implanted GaAs

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Abstract
Tellurium was implanted into Cr‐doped GaAs at 250 °C to a dose of 1013 or 1014 Te/cm2 at 120 keV. Sheet‐resistivity and Hall‐effect measurements were made on the samples for annealing temperatures up to 900 °C. From the temperature dependence of the sheet resistivity, the conduction mechanism of as‐implanted samples was found to be due to thermally assisted tunneling in disordered semiconductors. The very small activation energy of n‐type conductivity with the maximum effective bulk concentration being ∼1018 electrons/cm3 for the 1014 Te/cm2 sample annealed at 800 °C. However, the electrical compensation remained high (NA/ND ?0.6) for annealing temperatures ranging from 600 to 900 °C, the compensating centers being of the VGaTe‐complex type. The temperature dependence of the electrical characteristics for well‐annealed samples resembled that of bulk material. However, a somewhat larger value of donor ionization energy (∼7 meV) was obtained for the 1013 Te/cm2 sample annealed at 800 °C; this value may arise from the profiling effects.