Electrical properties of Schottky contacts to N-type ZnS _0.07Se_0.93 epilayers

Schottky contacts were formed on Cl-doped N-type lattice matching ZnS _0.07Se_0.93 epilayers grown on (100) N-GaAs substrates by molecular beam epitaxy for metals with different work functions, Yb, Al, Cr, Cu, Au, and Pd. Temperature-dependent current-voltage and capacitance-voltage (C-V) measurements show a clear relation between Schottky barrier height and metal work function which cannot be predicted by the linear Schottky contact theory, Φ_SB=Φ_M-χ. The pinning effect is believed to exist at the metal-semiconductor interface with a wide range of Fermi level pinning positions. Thermionic emission dominates the current transport mechanism and the current is limited by the ZnSSe/GaAs heterojunction under a relatively high positive bias. A symmetriclike C-V characteristic is explained by the Schottky barrier-heterojunction model and a fairly constant heterojunction barrier height, Φ_HJ, is obtained for Schottky diodes using different metals.