Relaxation models of the (110) zinc-blende III-V semiconductor surfaces: Density functional study

Clean III-V zinc-blende (110) surfaces are the most extensively studied semiconductor surface. For conventional III-V compounds such as GaAs and InP, the surface relaxation follows a bond rotation relaxation model. However, for III-nitrides recent study indicates that they follow a bond-constricting relaxation model. First-principles atom relaxation calculations are performed to explore the origin of the difference between the two groups of materials. By analyzing the individual shift trends and ionic properties of the top layer anions and cations, we attribute the difference between the conventional and nitride III-V compounds to the strong electronegativity of N, which leads to the s(2)p(3) pyramid bond angle to be larger than the ideal one in bulk (109.5 degrees). The general trends of the atomic relaxation at the III-nitrides (110) surfaces are explained.