Magnesium- and calcium-doping behavior in molecular-beam epitaxial III-V compounds

Residence lifetimes of Mg on GaAs surfaces were observed using 10 KV reflection electron diffraction and Auger electron spectroscopy to decrease from ∼120 s at 550 °C to ∼1 s at 600 °C. The electrical incorporation coefficient is ∼0.3 at and below 500 °C decreasing to ∼3×10−4 at 600 °C at the expense of desorption. Hole mobilities of uniformly Mg-doped samples are as good as those for equivalently Be-doped GaAs samples. Calcium does not behave as a shallow acceptor in GaAs grown by molecular-beam epitaxy.