First principle calculations of hydrogen in aluminium arsenide

Functional density calculations within the local density approximation and with ab-initio pseudopotentials of the properties of H in neutral and Sidoped AlAs have been performed. The equilibrium sites, the dependence of the stable charge state of H on the Fermi energy position and the bonding of H with Si-donors in AlAs have been investigated. It has been found that the equilibrium site for neutral H in AlAs is the hexagonal site in the low valence charge region. H behaves like a negative-U impurity, with a stable positive charge state in p-doped AlAs and a stable negative charge state in n-doped AlAs. The microscopic structure of the HSi donor complex is formed by an H in an antibonding position and a Si atoms largely displaced from its site towards the H. The calculated vibrational frequencies of the HSi compare well with the experimental results. © 1992.