Mott Barrier

A Mott barrier has a metal contact on a lightly doped surface layer on a more heavily doped substrate (Fig. 3.8). The lightly doped layer is fully depleted, and the space charge is negligible so that the electric field is constant. The capacitance of the device is small and independent of bias. The current, in this case, is diffusion limited rather than thermionic emission limited."

Metal-Insulator-Semiconductor Tunnel Diode

In the metal-insulator-semiconductor (MIS) structure, a thin interfacial layer such as an oxide is intentionally introduced before metal deposition (Fig. 3.9).20,21 The interfacial layer thickness lies in the range of 1-5 nm. The current is reduced from Eq. (3.5) to



where C, is the mean barrier height in eV, and S is the oxide thickness in nm (product is normalized to be dimensionless). The interfacial layer reduces the

majority-carrier current without affecting the minority-carrier current, and this

raises the minority injection efficiency. This structure is used in other devices

such as the solar cell, MISS switch, and surface oxide transistor.