Inverse photoemission from surface and interface states of III–V semiconductors

We have measured unoccupied surface and interface states on Ga- and In-derived III–V semiconductors with momentum-resolved inverse photoemission. The position of the surface states is found to be unrelated to the fundamental band gap. Instead, a connection with the gap of p-like states can be made. This finding is discussed in the context of theories of Fermi level pinning and band lineup, which use (virtual) gap states as a reference energy. Unoccupied metal-induced gap states are found for transition metals (Y, Ti, V, Mn, Pd) on GaAs(110) and InP(110). Their energy tracks the Fermi level pinning position, suggesting that these states are connected with the pinning process. A tentative assignment in terms of nonbonding metal d states is given.