Impurities in single crystal indium phosphide

The impurity concentrations in present low carrier concentration indium phosphide single crystals (N_D-N_A=2×10¹⁵ to 5×10¹⁵cm^–3) grown by the Czochralski technique have been measured by spark-source mass spectrometry and radio-gamma activation analysis and compared with both the polycrystalline source material and the excess indium produced during compounding and growth. The predominant impurities are shown to be carbon, oxygen and silicon but the segregation of lesser impurities into the excess indium has allowed some nineteen other elements which are likely to be present in indium phosphide to be identified. No consistent correlation is evident between the measured concentration of specific impurities and the ionized donor (N_D) and acceptor (N_A) impurity levels as determined from the free-electron concentration (N_D-N_A) and Hall mobility at 77 K using the Brooks-Herring theory.