A first-principles surface phase diagram study for Si-adsorption processes on GaAs(1 1 1) A surfaces

Abstract

The adsorption processes of an Si atom on GaAs(1 1 1) A surfaces under growth conditions are investigated on the basis of first-principles surface phase diagrams, in which adsorption–desorption behavior is described by comparing the calculated adsorption energy obtained by total-energy electronic-structure calculations with vapor-phase chemical potential estimated by quantum statistical mechanics. The calculated surface phase diagram as functions of temperature and As 2 pressure demonstrates that both Ga and As atoms are adsorbed on the Ga-vacancy site of GaAs(1 1 1) A- ( 2 × 2 ) surface under low As-pressure conditions, resulting in the formation of ( 2 × 2 ) surface with an As adatom. The surface phase diagrams as functions of temperature and Si pressure also reveal that an Si atom can be adsorbed on the ( 2 × 2 ) surface with an As adatom for temperatures less than ∼1160 K and this Si atom can occupy one of As-lattice sites after the incorporation of another As atom, leading to p-type conductivity. In contrast, the ( 2 × 2 ) surface with an As trimer is found to be stabilized under high As-pressure conditions. The surface phase diagram for Si incorporation clarify that an Si atom can be adsorbed at one of Ga-lattice sites of the ( 2 × 2 ) surface with an As trimer for temperatures less than ∼870 K. These calculated results provide one of possible explanations for the formation of p-type and n-type GaAs on GaAs(1 1 1) A surfaces under low and high As-pressure conditions, respectively.