WAVE-FUNCTIONS AND (110) SURFACE-STRUCTURE OF III-V-COMPOUNDS

New electron paramagnetic resonance determinations of the dangling orbital on Ga atoms on the cleavage surfaces of GaP are compared with corresponding data for GaAs and AlSb. Using a bond-orbital approach the (110) surface structure for all three compounds is reconstructed, with the surface cation withdrawing towards a near planar configuration with its three neighbors. The EPR results provide the first opportunity of experimentally evaluating surface-charge densities calculated by the pseudopotential method. Surface wavefunctions determined from the measurements are compared with the results of self-consistent pseudopotential calculations of GaAs surfaces, with and without the above reconstruction. It is concluded from this and other information, that current pseudocharge densities for surfaces are not reliable, due in part to the use of a local form of the pseudopotential.