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UBC Theses and Dissertations

Etching of Gallium Arsenide with atomic hydrogen Elzey, John W.


An optical interferometric method is used to make in-situ observations of continuous etching of the (100) GaAs surface during exposure to a known concentration of thermalised hydrogen atoms downstream from an H₂ plasma. Etch rates between 3 and 9 nm/min are followed at constant temperature within the range 229 - 360 °C. Increasing substrate temperature leads to increased rates of reaction. A Pt wire is used as an isothermal calorimeter to determine absolute H atom partial pressures on the order of 5 mTorr. Analysis of etch rate dependence on atomic hydrogen concentration verifies the surface reaction follows close to a first order rate law with respect to the hydrogen atom concentration and an Arrhenius analysis of the etch rate data yields an activation energy of 7(2) kcal/mol = 29(7) kJ/mol = 0.31(7) eV. Rate coefficients for the H + GaAs etching reaction were found in the aforementioned temperature range to have the temperature dependence kT = 10 ⁵⁷±⁰‧⁷ nm min⁻¹ Torr⁻¹ exp(-29±7 kJ/mol)/RT. Scanning electron microscope photomicrographs of etched samples reveal that large scale crystallographic etching occurs resulting in textured (100) GaAs surfaces and x-ray photoelectron spectroscopy demonstrated these surfaces were gallium-rich.

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