Surface structures of GaAs{111}A,B-(2 × 2)

Atomic structures of the GaAs{111}A,B-(2 × 2) surfaces have been studied using reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy (STM), and first-principles total-energy calculations. STM observations have revealed that the GaAs(111)A-(2 × 2) surface exhibits large ordered regions having the Ga-vacancy buckling structure, while the GaAs(111)B-(2 × 2) surface consists of small domains, where the As trimers are adsorbed on the outermost As layer. The atomic coordinates for both surface structures have been determined by a rocking-curve analysis using RHEED. The obtained structure parameters are in good agreement with those obtained from first-principles calculations.