Reactive scattering study of etching dynamics: HCl on GaAs(100)

Abstract

Pulsed supersonic molecular beam scattering has been used to study the inelastic scattering, trapping + desorption and reactive channels for the HCl + GaAs(100) thermal etching reactions. Temperature profiles of the reaction products GaCl, As₂ and Ga are reported in the range 600 to 883 K. Angular and time-of-flight (TOF) distributions of inelastically scattered and trapped + desorbed HCl are also reported. Angular distribution of all reaction products are described by a cosⁿ (θ) form with 0.95⩽n⩽1.4. The TOF distribution of GaCl reveals rapid production but with measurable time delay (50 μs–10 ms). The As₂ signals are effectively demodulated and correspond to delayed production on the surface with a time constant >1 s. A kinetic model initially proposed by Bent and colleagues (C. Su, Z. Dai, W. Luo, D. Sun, M. F. Vernon and B. E. Bent, Surf. Sci., 1994, 312, 181) is extended and provides excellent fits to the temperature profiles and the surface residence times for GaCl and As₂.