Tellurium - Modified surface states of GaAs(001) and InAs(001)

We investigate the stability and electronic structure of 1x2 and 2x2 GaAs(0 01):Te and InAs(001):Te surfaces with different degrees of tellurium covera ge (theta(Te) = 1/4, 1/2, 3/4 ,1), by means of first-principles pseudopoten tial calculations within density-functional theory. The adsorption stabilit y decreases as the tellurium coverage increases. The adsorption on InAs(001 ) is more stable than on GaAs(001). As-Ga. (or As-In) bonds for the uppermo st As atoms are s(2)p(2)-like (nearly planar), while the Te bonds at the su rfaces are sp(3)-like. The hetero-dimers in theta(Te) = 1/2 modify the char acter of GaAs(001):Te and InAs(001):Te surfaces resulting in a semiconducto r structure.