Hydrogen solubility in n-type silicon doped GaAs and its effects on the material electronic quality

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Abstract
Solubility of hydrogen in silicon doped GaAs has been investigated from deuterium diffusion experiments in buried silicon doped GaAs epilayers exposed to a deuterium plasma. The presence of silicon donors in the buried layer induces an increase of the solubility of hydrogen equal to the amount of active donors. Diffusion profiles after thermal annealing provide evidence that, in the buried doped layer, hydrogen is present at least in two forms: a mobile species, which is removed under annealing at 250 °C, 20 min, and a trapped form known to be Si-H complexes from infrared spectroscopic studies. The electron mobility of the annealed neutralized samples is systematically higher than in as-grown samples, for a given active donor concentration. For plasma conditions used for the fabrication of field effect transistors having a hydrogen neutralized active region, this holds true for buried layers protected by undoped GaAs cap layers as thin as 0.1 μm, then, the defects generated by the plasma are confined on a superficial layer less than 1000 Å.