HYDROGEN PASSIVATION OF CARBON-DOPED GALLIUM-ARSENIDE

The stability of a C atom at the cationic and anionic sites in GaAs and the hydrogen passivation of the C dopant activity have been investigated by performing first-principles total-energy calculations within the pseudopotential-density-functional-theory framework. In these calculations it is found that the C atom has almost the same stability at the gallium and at the arsenic sites. It is suggested that the preferred incorporation of C at the As site is due to phenomena occurring at the grown surface of GaAs. The H atom forms stable complexes with both the C acceptor (C(As)) and the C donor (C(Ga)). The H-C(As) and H-C(Ga) complexes show the same structural features despite previous theoretical results. They are both characterized by a stable configuration where the H atom is located at the bond-centered site by a strong H-C interaction and by negligible interactions of H with the host atoms. Present results give theoretical evidence of the hydrogen passivation of C donors and acceptors. Moreover, they suggest that hydrogen may form strong bonds with carbon and passivate its dopant activity even in other III-V semiconductors.