CLEAN AND AS-COVERED ZINCBLENDE GAN(001) SURFACES - NOVEL SURFACE-STRUCTURES AND SURFACTANT BEHAVIOR

We have investigated clean and As-covered zinc-blende GaN (001) surfac es, employing first-principles total-energy calculations. For clean Ga N surfaces our results reveal a novel surface structure very different from the well-established dimer structures commonly observed on polar III-V (001) surfaces: The energetically most stable surface is achiev ed by a Peierls distortion of the truncated (1 x 1) surface rather tha n through addition or removal of atoms. This surface exhibits a (1 x 4 ) reconstruction consisting of linear Ga tetramers. Furthermore, we fi nd that a submonolayer of arsenic significantly lowers the surface ene rgy indicating that As may be a good surfactant. Analyzing surface ene rgies and band structures we identify the mechanisms which govern thes e unusual structures and discuss how they might affect growth properti es.