Etching of Gallium Arsenide with atomic hydrogen

• Main Author: Elzey, John W.
• Format: Others
• Language: English
• Published: 2008
• Online Access: http://hdl.handle.net/2429/1357

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. === Science, Faculty of === Physics and Astronomy, Department of === Graduate