CHANNELING CHARGED-PARTICLE ACTIVATION-ANALYSIS OF LIGHT IMPURITIES AT TRACE LEVELS IN GAAS

Light element trace concentrations of boron, carbon and oxygen in the range of 10 to 150 ppba were localized in monocrystalline, as-grown GaAs by combining the channeling technique with the sensitivity of charged particle activation analysis (CPAA). The experimental data were evaluated using stopping power and ion flux distributions in the crystal channels that were simulated with the Monte Carlo program MABIC (materials analysis by ion channeling) [1]. Si samples have been used as a reference material. The B and O concentrations of the Si samples are in the range of 100 ppma and 8 to 40 ppma respectively. In GaAs trace concentrations of boron, carbon and oxygen were found to be located preferentially in an interstitial position. In Si boron was localized mainly on substitutional sites for concentrations in the 100 ppma range. Oxygen concentrations of 8 to 40 ppma in Si were determined to be dominantly incorporated on interstitial positions.