Theory of semiconductor surface states and metal–semiconductor interfaces

The electronic structure of vacuum–semiconductor and metal–semiconductor interfaces has been studied using a method involving self-consistent pseudopotentials. Our model for an intimate metal–semiconductor interface consists of jellium in contact with a semiconductor described in the pseudopotential formalism. Local density of states and charge densities are used to analyze the electronic properties of the two types of interfaces. For the vacuum–semiconductor case, Si (111) surfaces and the (110) surfaces of III–V and II–VI zincblende semiconductors are investigated, with GaAs and ZnSe considered as zincblende prototypes. For metal–semiconductor interfaces, jellium of Al density in contact with (111) surfaces of Si and the (110) surfaces of GaAs, ZnSe, and ZnS are investigated. The calculated Schottky barrier heights are in good agreement with experimental results. It is shown that the variations in the experimental barrier height for different metals in contact with various semiconductors can be understood in terms of a simple model using the result of the pseudopotential calculations. The relation of our results to other theories and current experiments is discussed.