Current transport mechanisms in atomically abrupt metal-semiconductor interfaces

A comprehensive model for electron transport mechanisms across a fully formed Schottky-barrier junction is proposed in which the metal-semiconductor interface is approximated as an abrupt quantum mechanical transition. Improved formulations of the barrier-lowering mechanisms and carrier tunneling effects are derived where the dipole barrier lowering is modeled as a single exponential decay of the total surface charge density. Quantum calculations follow a two-band model in which the imaginary component of the electron wave vector in the semiconductor energy gap is obtained by including the effect of both conduction and valence states. The energy band profile effects are included in the calculation of tunneling current, and it is shown that the finite negative charge residing at the metal-semiconductor interface considerably modulates the tunneling transmission probability of carriers. Experimental results obtained from atomically clean Al-n⁺ GaAs-nGaAs interfaces fabricated by in situ molecular-beam epitaxy (MBE) are shown to be in excellent agreement with the transport calculations