Ion channeling in GaAs: Be, Mg, Zn, and Cd, and calculations of electronic stopping powers

Abstract

Atom depth distributions measured by secondary ion mass spectrometry are reported for 9Be, 24Mg, 64Zn, and 114Cd channeled in the GaAs crystal. The ion energies were 150 or 300 keV and the fluences were 3.0×1013 cm−2. Fairly well-defined maximum ranges are observed in the 〈110〉 profiles for three of these four acceptor impurities in GaAs. The Mg and Zn profiles are deep because of the low electronic stopping and no peak is observed in the deep channeled region of the profiles. The 〈110〉 Be profile is flat within a factor of about two over most of the range, but the deep portion is rounded and does not decrease sharply at the maximum range as it does for Si, S, Se, Cd, and Te. These data are combined with those reported previously for Si, S, Se, and Te, and the maximum ranges in the 〈110〉 and 〈100〉 channeling orientations are used to calculate values of the electronic stopping Se and the coefficient k, based on the assumption of velocity- proportional electronic stopping (Se = kE0.50).