Evidence for the creation of the main electron trap in bulk GaAs

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Abstract
Ikoma and Tanigushi have recently proposed a procedure consisting of O or As ion implantation followed by a 600 °C anneal to create a midgap electron trap in GaAs. The question of the definite identification of this level with the native level EL2, the main electron trap always observed in bulk and vapor phase epitaxial materials, remained open. To answer this question, we performed photocapacitance transient experiments. In these experiments, the presence of EL2 is revealed unambiguously by an overshoot behavior in the photocapacitance transients. We have reproduced the experiment of Tanigushi and Ikoma using O, B, and Ne as implanted species. Our experiment has established that EL2 is created by O, B, or Ne implantation in bulk GaAs. When the same procedure is repeated with liquid phase epitaxial material, an electron trap is created at approximately the same energy level but the photocapacitance transient experiment shows that this level does not have the same properties as EL2.