Carbon, oxygen and silicon impurities in gallium arsenide

The concentrations of carbon, oxygen and silicon, together with boron, aluminium, sulphur and potassium, in various samples of bulk gallium arsenide have been determined by spark source mass spectrometry (SSMS) calibrated by independent chemical methods. Hall effect measurements and localised vibrational mode (LVM) infrared absorption measurements have been made on the same samples. It is inferred that the carbon atoms which show LVM absorption are located on arsenic lattice sites and act as acceptors. Calibrations for the LVM lines for C AS , Si Ga , Al Ga and B Ga have been obtained. All samples examined contained a very low concentration of oxygen in the range (1-4)*10 15 cm -3 . Carbon concentrations of up to 10 17 cm -3 were measured in deliberately doped material, while other crystals contained levels of 5*10 15 cm -3 or lower.