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Room temperature characteristics of Schottky diodes with different Schottky contact metals on both -type and -type Ge. The inset shows the Richardson plots of the -type Ge, -type Ge, and -type Ge Schottky diodes under the reverse bias, from which the Schottky barrier heights are determined to be 0.54, 0.62, and , respectively.
(a) Room temperature characteristics of -type and -type (inset) Ge Schottky diodes of various Al oxide layer thicknesses. By insertion of the Al oxide interfacial layer, the characteristics change from rectifying to quasi-Ohmic for -type diodes, while from Ohmic to rectifying for -type ones. (b) The left axis shows the Schottky barrier heights of -type and -type Ge Schottky diodes with various Al thicknesses. The right axis shows the forward and reverse current densities of -type Schottky diodes with various Al thicknesses.
Schottky barrier heights of the -type Ge Schottky diodes vs the metal work functions, with and without the insertion of an interfacial Al oxide layer. Without the Al oxide layer, the Schottky barrier heights of all three metals are pinned close to the Ge valence band. After insertion of an Al oxide layer, the Schottky barrier heights decrease to 0.39, 0.23, and for Ni, Co, and Fe Schottky diodes, respectively. However, the ideal Schottky–Mott relation (dash line) was never observed.
Schematics of the band diagram of (a) a strongly pinned Schottky contact and (b) a pinning-alleviated contact by insertion of a thin tunneling oxide.
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