Open Collections

Abstract

The reaction of gallium arsenide {100} with molecular and atomic bromine was studied at temperatures between 100 and 225°C and at pressures of bromine between 0.1 and 40 Torr. Samples of GaAs were placed on a silicon platform within a Pyrex reactor flow system and the etch rate was determined by profilometry or weight change of the sample. Atomic bromine was produced by a 2450 MHz microwave discharge and the samples were etched downstream. The atomic concentration was measured by an isothermal calorimetric detector. Pressure dependence studies for molecular Br₂ etching showed that below 1-2 Torr of bromine, a first order reaction was rate-limiting whereas above this pressure a half order reaction was rate-limiting. Temperature dependence studies for the low pressure and high pressure regimes gave activation energies and pre-exponential values for the two respective rate controlling reactions. The first order reaction was found to have an activation energy of 29.2 ±4.0 kJ mol⁻¹ and a pre-exponential value of (3.4 ± 4.4) x 10²¹ molecule cm⁻² s⁻¹ Torr⁻¹. The activation energy for the half order reaction was found to be 8.4 ± 0.7 kJ mol⁻¹ with a pre-exponential of (6.4 ± 1.3) x 10¹⁸ molecule cm⁻² s⁻¹ Torr⁻¹⁄². The activation energy for atomic etching was calculated to be 12.9 ± 0.9 kJ mol⁻¹ and the pre-exponential, (7.1 ± 2.0) x 10²⁰ atom cm⁻² s⁻¹ Torr⁻¹.