QUASI-ONE-DIMENSIONAL STRUCTURES AND METALLIZATION FOR THE DEPOSITIONOF K ON GAAS(100) AS-RICH SURFACES

A local-density linear combination of atomic orbitals method has been applied to study the deposition of a K overlayer on the As-rich GaAs(1 00)-2 x 4 reconstruction. Our results show that the K atoms form quasi -one-dimensional structures along the missing rows of the semiconducto r surface. The conduction band associated with the K orbitals is analy zed by means of an extended Hubbard Hamiltonian. We show that a Mott t ransition appears for a deposition of 6-7 K atoms per unit cell, and a rgue that for this coverage the metal-semiconductor barrier is almost completely formed.